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The Weining Beishan area of Ningxia Hui Autonomous Region is located at on the western edge of the Helanshan tectonic belt, which is a tectonic joint among Alxa Block, Ordos Block, and North Qilian orogenic belt. However, the tectonic evolution of this area remains unclear due to the lack of magmatic information. This paper conducted researches on geochronology, geochemistry, and Sr-Nd-Hf isotopes of the diorite porphyrites exposed in the Weining Beishan area. The zircon U-Pb dating yields two ages of 145.0 ± 1.1 and 146.2 ± 1.5 Ma, and the whole-rock geochemical data indicate that the diorite porphyrites are metaluminous to weakly peraluminous and high-K calc-alkaline series. The characteristics of highly initial 87Sr/86Sr ratios (0.708 16 to 0.710 47), negative εNd(t) (−8.9 to −8.4), and negative εHf(t) (−13.8 to −21.2) indicate that the diorite porphyrites originated from partial melting of the middle-lower ancient crust related to the North China Craton. Combined with the regional geology, we suggested that partial melting was triggered by a tectonic activity of deep faults cutting through the crust under the regional stress transformation from compressing to extension during the Late Jurassic–Early Cretaceous, which is probably related to the westward subduction of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

A tectonic switch from subduction to collision and/or arc–arc collision is a key issue for understanding accretionary orogenic processes. We present new U-Pb ages, geochemistry, whole-rock Nd and zircon Hf isotope data for a suite of late Carboniferous intrusive rocks along the Kalamaili suture zone of the southwestern Central Asian Orogenic Belt (CAOB) and demonstrate their petrogenesis and the transition of their tectonic settings. Zircon U-Pb dating for the gabbros, diorites, granodiorites, and monzogranites yields ages of 317–301 Ma. The gabbros (311 Ma) were likely derived from partial melting of a mixed source of depleted MORB-like asthenospheric mantle with minor old crustal material; the diorites (301 Ma) from the mixed depleted lithospheric mantle and crustal components; the granodiorites (303 Ma) from the mixed mantle- and crust-derived magmas; and the monzogranites (317 Ma) from melting of the newly underplated basaltic lower crust. Combined with previous data, we have grouped all the intrusive rocks along the Kalamaili suture zone into three phases: 350–340 Ma, 330–320 Ma, and 320–300 Ma. The first phase consists of tholeiitic and high-K calc-alkaline granites, the second phase is composed of high-K calc-alkaline I-type granites with strong deformation, and the third phase comprises voluminous and various rock types (mainly mafic and felsic, including many A-type granites), revealing a magmatic flare-up. The magmatic associations and evolution from the first to the third phase, together with regional geology, suggest a tectonic transition from subduction/accretion (350–340 Ma) through syn-collision (330–320 Ma) to post-collision (or post-accretionary, 320–300 Ma), respectively. This study provides new magmatic evidence for the switch from subduction to collision (arc-arc collision) along the Kalamaili suture zone in the southwestern CAOB. [ABSTRACT FROM AUTHOR]

The tectonic transition from oceanic subduction to continental collision is a fundamental process during orogenesis, yet the nature of such transition and associated deep geodynamic processes for the Tibetan Plateau are still controversial. The long‐lived magmatism of the Gangdese Belt of southern Tibet provides an excellent opportunity to study the tectonic transition from subduction of the Neo‐Tethys oceanic lithosphere to the continental collision between Indian and Asian plates. We present zircon U–Pb–Hf isotopes, whole‐rock geochemistry, and Sr–Nd isotopes for the intrusions from Maizhokunggar, southern Lhasa Terrane. The zircon U–Pb dating indicates that two episodes of magmatism occurred in the Maizhokunggar region, ca. 70 Ma diorites and ca. 60 Ma granitoids. The ca. 70 Ma diorites are medium‐K calc‐alkaline and characterized by pronounced high‐field‐strength element depletion and light rare earth element enrichment, similar to arc‐type rocks. They have homogeneous (87Sr/86Sr)i ratios (0.70378–0.70424) and εNd(t) values (+2.6 to +3.4), and εHf(t) (+5.9 to +13.0) with relatively young depleted mantle model ages (307–762 Ma), suggesting that they were generated from the juvenile mafic lower crust induced by the underplating of basaltic magmas from depleted mantle wedge. The ca. 60 Ma granitoids, Kajiacun (KJC) granodiorites, and Qulongxue (QLX) and Bangdacun (BDC) monzogranites are high‐K series and metaluminous to weakly peraluminous. The KJC granodiorites with high Sr/Y ratios (25–43) are adakitic and were likely derived from partial melting of a thickened lower crust. The BDC monzogranites have more evolved Sr–Nd–Hf isotopes and older Nd–Hf model ages than the QLX monzogranites. These geochemical variations were mainly controlled by the fractionation crystallization with assimilation of ancient crustal materials. We propose that at ca. 70 Ma, the subduction of the Neo‐Tethys oceanic slab triggered the partial melting of the juvenile lower crust and formed the diorites with arc affinity, and then the initial collision (>60 Ma) between the Indian and Asian plates caused locally thickened lower crust, resulting in adakitic granodiorites. Our study sheds light on the lithospheric scale magma evolution from the deep mantle to the shallow crust during the critical geodynamic transition to collision, and early uplift. [ABSTRACT FROM AUTHOR]

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Dongnan Cu–Mo deposit, located in the southeast of the Zijinshan ore field (the largest porphyry–epithermal system in Southeast China), represents the complex magmatic and metallogenesis events in the region. The petrogenesis and metallogenesis of granitoids from the deposit are not determined, especially the interactions between ore-bearing (granodiorite porphyry) and barren samples (granodiorite and diorite). In the paper, the whole rock geochemical features shared a similar affinity to the middle-lower content and revealed that they derived from partial melting of the Cathaysian basement with the contribution of mantle materials, even represented that they generated in the plate subduction; LA-ICP-MS zircon U–Pb ages show that these granodiorites, granodioritic porphyry and diorite, were generated during 114–103 Ma. The ore-bearing samples mostly presented εHf(t) of negative values (peak value is −4 to −3) with old two-stage Hf model ages (tDM2) (peak value is 1.10–1.15 Ga), while the barren sample showed slightly negative εHf(t) (peak value is −1 to 0) values with young tDM2 (peak value is 1.00–1.05 Ga). The value of zircon Ce4+/Ce3+ ratio mostly higher than 450 was first verified for the ore-bearing samples in the Dongnan Cu–Mo deposit, and the values of ore-bearing were found to be higher than those from the barren, which suggests that the ore-bearing formed in more oxidized parental magma with higher oxygen fugacity. Based on the geochemical characteristic of the element and isotope, we concluded that the Early Cretaceous multi-phases magmatic activities, low melting temperature and low pressure of pluton, and high oxygen fugacity of zircon, were the favorable conditions for metallogenesis of Dongnan Cu–Mo deposit. [ABSTRACT FROM AUTHOR]

The granite complex in the Maohuo area of Litang County is located in the central and western parts of the Yidun-Shaluri island arc in the Sanjiang area; the intrusion is located in the sand slate of the Tumugou Formation in Daocheng District. In this paper, the petrographic analysis of the granodiorite porphyry and biotite monzogranite in the granite complex in the Volcano area is carried out, a systematic study of rock geochemical characteristics and chronology, elucidating the genetic connection between the two in the nature and tectonic background of the source region. Zircon LA-ICP-MS U–Pb dating shows, granodiorite porphyry, medium-coarse-grained biotite monzogranite, the ages of diorite inclusions in biotite monzonitic granites are 220.7 ± 1.3 Ma, 220.4 ± 1.6 Ma, and 219.8 ± 1.4 Ma, three are roughly formed at the same time, and it is a product of late Triassic magmatic activity. Rock geochemical features show that granodiorite porphyry in the granite complex, biotite monzonite granite, scintillation inclusions it has high total alkali, Rb content and relatively low Al2O3, Sr and other content, has a moderately negative europium anomaly, obvious loss of Ta, Nb, Ti and other high field strength elements, and aluminum saturation index < 1.1 is characterized. Combined with geological data granodiorite porphyry, both biotite monzonitic granites are also I-type granites formed in a typical island-arc environment. Combined with rock geochemical characteristics and U–Pb chronology research results, three should be a set of rock assemblages formed by the evolution of a set of magma melting events. Among them, biotite monzogranite and granodiorite porphyry are the products of homologous magma crystallization and differentiation. The diorite enclaves in the biotite monzogranites are the result of their own evolution when the granitic magma undergoes fusion and immiscibility. [ABSTRACT FROM AUTHOR]

The Kaimuqi area in the Eastern Kunlun Orogen (EKO) contains many lherzolite, olivine websterite, gabbro and diorite intrusions, and new zircon U–Pb dating, Lu–Hf isotope and whole-rock geochemical data are presented herein to further confirm the Late Triassic mafic–ultramafic magmatism with Cu–Ni mineralization and to discuss the petrogenesis and geodynamic setting. Zircon U–Pb dating shows that the Late Triassic ages, corresponding to 220 Ma and 222 Ma, reveal the mafic–ultramafic and dioritic magmatism in Kaimuqi, respectively. Zircon from gabbro has εHf(t) values of −3.4 to −0.2, with corresponding TDM1 ages of 994–863 Ma. The mafic–ultramafic rocks generally have low SiO2, (Na2O+K2O) and TiO2 contents and high MgO contents and Mg# values. They are relatively enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depleted in heavy REEs (HREEs) and high-field-strength elements (HFSEs), indicating that the primary magma was derived from the metasomatized lithospheric mantle. The diorites show sanukitic high-Mg andesite properties (e.g., MgO = 2.78%–3.54%, Mg# = 50–55, Cr = 49.6–60.0 ppm, Sr = 488–512 ppm, Y = 19.6–21.8 ppm, Ba = 583–722 ppm, Sr/Y = 23.5–25.4, K/Rb = 190–202 and Eu/Eu* = 0.73–0.79), with LREEs and LILEs enrichments and HREEs and HFSEs depletions. We suggest that the primary Kaimuqi diorite magma originated from enriched lithospheric mantle that was metasomatized by subduction-derived fluids and sediments. The Kaimuqi mafic–ultramafic and dioritic intrusions, with many other mafic–ultramafic and K-rich granitic/rhyolitic rocks in the EKO, formed in a dynamic extensional setting after the Palaeo-Tethys Ocean closure. [ABSTRACT FROM AUTHOR]

East Junggar is an important part of the Central Asia Orogenic Belt and has developed a multi‐epoch and multi‐type metallogenic system. Yundukala is a recently discovered large intrusion‐related Au–Cu–Co deposit. The No. 1 main mineralization zone mainly occurs in the contact area between fine‐grained diorite and basalt. Massive and vein mineralization have developed there, but the ore‐bearing stratum, ore‐bearing intrusive rocks, and metallogenic ages are not clear. Zircon SHRIMP U–Pb dating of the porphyritic diorite and fine‐grained diorite yields ages of 416.1 ± 3.9 Ma and 411.1 ± 7.5 Ma, respectively. The dioritoid intruded into the ore‐bearing stratum, indicating that this formation is part of the Early Palaeozoic strata rather than the Middle Devonian Beishan Formation. The Re–Os isochron age of the chalcopyrite in the massive mineralization is 402.6 ± 5.2 Ma; thus, the massive mineralization is related to fine‐grained diorite and formed in the Early Devonian. Six sulphides and four sulphides from the vein mineralization yield Re–Os isochron ages of 352.8 ± 1.8 Ma and 354 ± 23 Ma, respectively, and the limited vein mineralization was formed during 353–354 Ma. The massive and vein mineralizations in the Yundukala deposit were formed in the Early Devonian and Early Carboniferous. [ABSTRACT FROM AUTHOR]

The subduction of the Proto-Tethyan Ocean is still a controversial subject. Here we report zircon U-Pb ages, geochemistry, and Hf isotopic compositions of the zircon in the Mengkete quartz diorite in the Buqingshan–A'nyemaqen Tectonic Mélange Belt, which lies at the southern margin of the East Kunlun orogenic belt on the northern Tibetan Plateau, to constrain the petrogenesis of subduction-related granitoids and to reconstruct the evolution of the Buqingshan–A'nyemaqen Ocean. Zircons U-Pb dating yields coeval ages of 441–436 Ma for Mengkete quartz diorite. Mengkete plutons have variable SiO2 (56.63–65.22%) and high Al2O3 (16.09–17.79%) contents and aluminous saturation indexes (A/CNK ratios) ranging from 0.77 to 0.96, which define their metaluminous and medium-K2O calc-alkaline signatures. The plutons have a low total rare-earth element (REE) content (45.49–168.31 ppm) and slightly positive Eu anomalies (Eu/Eu* in the range of 0.96 to 1.32). They are also enriched in large-ion lithophile elements (LILEs), such as Rb, Th, and Ba, but are depleted in high-field-strength elements (HFSEs), such as Nb, Ta, Zr, Hf, and Ti. Their zircon εHf(t) values ranging from 7.79 to 13.02, and the two-stage Hf (TDM2) model ages are in the range of 1130–657 Ma. These geochemical signatures indicate that the Mengkete quartz diorite was derived from partial melting of the mafic Meso-Neoproterozoic lower crust during the northward subduction of the Proto-Tethyan Ocean. The evolution of the East Kunlun Belt can be divided into five stages from the Neoproterozoic to late Middle Triassic: (1) an opend Buqingshan‒A'nyemaqen ocean during the Neoproterozoic up to 516Ma; (2) the continuous expansion of the Buqingshan‒A'nyemaqen ocean during the period 516 to 441Ma, along with the beginning of northward subduction in the Late Cambrian; (3) further subduction from 441 to 400Ma, accompanied by the production of large volumes of arc magmatic rocks; (4) the long period during which the Buqinshan–A'nyemaqen Ocean existed (400–240 Ma); and (5) the final closure of the Buqinshan–A'nyemaqen Ocean in the late Middle Triassic. [ABSTRACT FROM AUTHOR]

BACKGROUND: Apatite is a common U - bearing accessory mineral with a U - Pb closure temperature of ~500℃, making U - Pb dating of apatite a potentially valuable thermochronometer. However, its low U concentration, high common lead concentration and lack of reference material has limited widespread application to LA-ICP-MS dating. OBJECTIVES: To develop a technique for U-Pb dating of apatite using laser ablation sector field inductively coupled plasma-mass spectrometry (LA-HR-ICP-MS). METHODS: The U-Pb isotope ratio in apatite samples was determined by LA-HR-ICP-MS, with apatite MAD2 as the external standard to correct U - Pb and Pb - Pb elemental fractionation directly without a common Pb correction. RESULTS: Long-term U-Pb analysis of Madagascar apatite sample (MAD2) showed homogeneous distribution of U, Pb and U-Pb isotope ratios, with average contents of U and Pb ~ 23. 8×10 -6 and ~ 13. 5×10 -6, respectively and weighted average 207 Pb / 206 Pb and 206 Pb / 238U ratios of 0. 0941±0. 0006 and 0. 0794±0. 0004, respectively. Taking MAD2 apatite as a reference mineral, combined with 207 Pb-correction method, the ages of apatite samples, McClure Mountain (521±5Ma), Tory-Hill-apt (1021±16Ma), a Durango (30. 7±1. 5Ma) and Fagnshan diorite apatite (~131Ma) can be determined accurately. CONCLUSIONS: The Madagascar apatite sample (MAD2) can be used to calibrate apatite U-Pb isotope ratio measured by LA-ICP -MS directly, without common-Pb correction, similar to the calibration strategy in zircon U-Pb dating. The method greatly reduces the difficulty of data processing during apatite U-Pb dating by LA-ICP -MS, which is conducive to the wide application of the method. [ABSTRACT FROM AUTHOR]

The timing of the Lhasa–Qiangtang collision following the closure of the Bangong–Nujiang Tethys Ocean has not been well constrained. An integrated study of whole-rock geochemistry and zircon U–Pb–Hf isotopes was carried out for Early Cretaceous quartz diorite-porphyrites and granites from the Yilashan and Amdo areas, northern Tibet. LA–ICP–MS zircon U–Pb dating reveal that the Yilashan and Amdo granitoids were emplaced at ~121–110 Ma. These granitic rocks display selective enrichment of light rare earth elements, large ion lithophile elements (e.g., Rb, U) and Th, but depletion of Sr and high field strength elements (e.g., Nb, Ta, Ti) compared to its neighboring elements. These new data, combined with regional geological setting, show that these igneous rocks were formed under a geodynamic setting of the Lhasa and Qiangtang (–Amdo) collision with oceanic slab breakoff and asthenospheric upwelling. The BNTO had been closed at ~121–110 Ma in the study area. Yilashan-Amdo granitoids roughly yield high (87Sr/86Sr)i ratios and obvious negative εNd(t) and zircon εHf(t) values along with old Nd TDM and zircon Hf TDM2 ages. Together with their variable U–Pb ages, these features indicate a Precambrian "hidden" crustal source beneath the northern Lhasa and Amdo terranes. The YLSS S-type granophyres were derived from partial melting of Paleoproterozoic lower crustal metagraywackes, whereas the YLSZ quartz diorite–porphyrites and the Amdo I- and A-type granites were mainly derived from partial melting of Paleo–Mesoproterozoic lower crustal mafic rocks with a certain amount of addition of mantle-derived melts. Minor amounts of the materials originated from the Amdo orthogneisses may also be involved in the formation of the YLSZ quartz diorite–porphyrites and the Amdo I-type granites. In addition, the Yilashan ophiolite was intruded by the ~112–108 Ma granophyric and quartz diorite–porphyritic intrusions before its final emplacement into the surrounding strata. [ABSTRACT FROM AUTHOR]

The large Bayanbaolege Ag polymetallic ore deposit is located in the Tuquan-Linxi Fe (Sn)-Cu-Pb-Zn-Ag-Nb (Ta) polymetallic metallogenic belt, which is an important part of the Great Xing'an Range metallogenic province, northeast China. The sulfide–quartz vein-type orebodies in the deposit are mainly hosted in the Cretaceous granodiorite porphyry and Late Permian Linxi formation. The U-Pb dating of the zircon from the post-ore diorite porphyrite yields an age of 124.8 ± 1.1 Ma, which constrains the mineralization time at the Early Cretaceous. The Sr-Nd isotope values (87Sr/86Sr)i = 0.708576~0.710536; εNd (t) = −0.51~+0.69; the Hf isotope values 176Hf/177Hf = 0.2827278~0.2830095, the εHf (t) = +3.1~+11.2, TDM2 = 615~1341 Ma of the metallogenic granodiorite porphyry. The Hf isotope values 176Hf/177Hf = 0.2828596~0.2829451, and the εHf (t) = +5.7~+8.8 of the diorite porphyrite, TDM2 = 827~1108 Ma, indicating that the ore-forming materials were the possible involvement of heterogeneous juvenile sources including moderately depleted mantle and newly underplated lower crust. The major and trace elements (including REEs) implied that these intrusions are the I-type granite and linked intimately to the westward subduction of the Paleo-Pacific Ocean plate. From these whole-rock major and trace elements and zircon U-Pb ages, as well as Sr-Nd-Hf isotope data, we conclude that the ore-associated I-type granites in the Bayanbaolege deposit formed in an extensional tectonic setting of the Early Cretaceous, and are compactly related to the retreat of the Paleo-Pacific Ocean subducted plate linked intimately to the westward subduction of the Paleo-Pacific Ocean plate rather than the closure of the Mongol–Okhotsk Ocean. Furthermore, by integrating geological background work and previous research work, implying the mineralization age of the Bayanbaolege deposit should have been formed in the 125–130 Ma. [ABSTRACT FROM AUTHOR]

The East Kunlun Orogenic Belt is located in the western part of the Central Orogenic Belt of China, with a large number of Triassic igneous rocks parallel to the Paleo-Tethys ophiolite belt, which provides a large amount of geological information for the tectonic evolution of the Paleo-Tethys Ocean. The granitoids studied in this paper are located in the Ela Mountain area in the eastern part of the East Kunlun Orogenic Belt. Zircon U-Pb dating results show that these different types of granitoids were crystallized in the Triassic. The 247.5 Ma porphyritic granites from Zairiri (ZRR) displayed calc-alkaline I-type granite affinities, with the zircon εHf(t) values being mainly positive (−0.5 to + 3.8, TDM2 of 1309–1031 Ma), indicating that they are derived from the partial melting of the juvenile crust and mixed with ancient crustal components. The 236.8 Ma Henqionggou (HQG) granodiorites and 237.5 Ma Daheba (DHB) granodiorites are high-K calc-alkaline I-type granite, and both have mafic microgranular enclaves (MMEs), showing higher and more varied Mg# (39.73–62.73), combined with their negative Hf isotopes (εHf(t) = −2.6 to −1.6, TDM2 = 1430–1369 Ma), suggesting that their primary magmas were the products of partial melting of the Mesoproterozoic lower crust that mixed with mantle-derived rocks. The 236.4 Ma DHB porphyritic diorites showed characteristics of high-K calc-alkaline I-type granitoids, with moderate SiO2 contents, medium Mg# values (40.41–40.65), with the Hf isotopes (εHf(t) = −2.9 to −0.5; TDM2 = 1451–1298 Ma) indistinguishably relative to contemporaneous host granodiorites and MMEs. The petrographic and geochemical characteristics indicate that the porphyritic diorites are the product of well-mixed magma derived from the Mesoproterozoic lower crust and lithospheric mantle. Based on the results of this paper and previous data, the chronology framework of Late Permian–Triassic magmatic rocks in the eastern part of the East Kunlun Orogenic Belt was constructed, and the magmatic activities in this area were divided into three peak periods, with each peak representing an extensional event in a particular tectonic setting, for example, P1 (slab roll-back in subduction period; 254–246 Ma), P2 (slab break-off in transition period of subduction and collision; 244–232 Ma), P3 (delamination after collision; 230–218 Ma). [ABSTRACT FROM AUTHOR]

The East Kunlun Orogenic Belt (E‐KOB) of the northern Tibetan Plateau is an accretionary orogenic belt, which has experienced complicated tectonic evolutionary processes of the Proto‐ to Palaeo‐Tethys Ocean. The Muztagh‐Buqingshan‐Anemaqen ophiolitic mélange zone (MBAM) is an accretionary complex related to the northward subduction of the Tethyan Ocean. Numerous intrusions outcropped in MBAM have witnessed the long‐term subduction‐accretionary process and thus site the key to comprehending the tectonic evolution of the E‐KOB, as well as the Tethyan Ocean. In this study, petrological, geochronological, and geochemical studies of the Marzheng diorites in the MBAM were carried out to explore the Early Palaeozoic tectonic evolution of the E‐KOB. Zircon U–Pb dating analysis suggests that the diorites were formed in the Early Ordovician at ca. 470 Ma. Furthermore, the εHf(t) values (5.3–14.1), Mg# values (39.7–51.2), and Nb/Ta (12.8–14.8), Zr/Hf (33.8–44.8), and Lu/Yb (0.15–0.16) ratios are generally close to those of depleted mantle‐derived rocks and the diorites were originated from a depleted asthenosphere mantle source. In addition, these diorites are characterized by enriched light rare earth elements (LREEs) (La and Nd) and depleted high‐field‐strength elements (HFSEs) (Nb, Ta, P, and Ti), similar to the fingerprints of arc‐related gabbroic‐dioritic rocks. This is also consistent with their high H2Omelt (6.0–8.3%) and oxygen fugacity (logfO2 = −14.3 to −13.5) features, indicating that they were formed in a subduction‐related setting. Our new investigations suggest that the Proto‐Tethys Ocean in the East Kunlun was still actively subducting northward during the Early Ordovician. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A "porphyroclast" system occurred in the Tuwu area in the late Early Permian. • The dextral shear event within the Kangguer Shear Zone was initiated at ca. 278 Ma. • The event provides constraints to the intracontinental convergence of the East Tianshan. The Kangguer Shear Zone, located in the East Tianshan, is one of the key faults for understanding the final amalgamation processes of the southwestern margin of the Central Asian Orogenic Belt. Magmatism was active in the Tuwu area of the Kangguer Shear Zone during the late Early Permian. LA–ICP–MS U–Pb dating analyses of the magmatic zircons from three monzogranite plutons, a felsic dyke, and a diorite dyke show ages of 286.9±0.78, 282.8±0.62, 281.7±0.89, 278.0±0.61, and 278.1±1.2 Ma, respectively. Detailed field and microscopic observations reveal that these intrusions form a "porphyroclast" system, and this area has undergone ductile dextral strike-slip deformation, with foliations dipping steeply to the south and subhorizontal stretching lineations trending to the east. Further structural analysis indicates that the three monzogranite plutons intruded into the Kangguer Shear Zone and cooled into rigid bodies before regional dextral strike-slip deformation, which limited the deformation that occurred after 282 Ma. The felsic dykes exhibit synkinematic characteristics, and the diorite dyke may have intruded before or at the same time as dextral strike-slip deformation, implying that regional dextral shear was initiated at ca. 278 Ma. These data, combined with previous studies, suggest that the initiation of dextral shear in the Kangguer Shear Zone occurred after the closure of the Kangguer Ocean and was the result of regional nearly N–S compression caused by the convergence of the Tarim Craton and plates north of the Kangguer Shear Zone. [ABSTRACT FROM AUTHOR]

High-Mg andesites (HMAs) and their cognate intrusive rocks constitute volumetrically very small proportions of the total earth, and are mainly distributed along the edges of convergent plates. Petrogenetic studies can provide possible solutions for discrepancies in the geodynamics and subduction zone evolution. This paper presents the first ever reports of the newly discovered high-Mg diorite in Akechukesai area, the western part of the East Kunlun Orogenic Belt, and provides a reference for the evolutionary history and subduction mechanism of the Proto-Tethys Ocean. Akechukesai high-Mg diorites yielded a weighted mean zircon U-Pb dating age of 427.3 ± 2.3 Ma (Middle Silurian). Results of the geochemical analyses show that the high-Mg diorites were high-K calc-alkaline series with the SiO2 content ranging 50.40 to 55.41 wt%. They are characterized by high values of Mg# (67–77), high MgO (6.92–10.58 wt%), TiO2 (0.53–0.87 wt%), Cr (286–615 ppm), Ni (61–124 ppm), Ba (570–927 ppm) contents, and low FeOtotal/MgO ratios (0.54–0.89). Furthermore, they exhibit nearly flat right-declined rare-earth element (REE) patterns with slight LREE enrichment. The samples are enriched in large ion lithophile elements (e.g., Ba, Rb, and Th) and depleted in high field strength elements (e.g., Ta, Nb, and Ti). These geochemical features are analogous to the sanukitic high-Mg andesites. The mean value of the initial εHf(t) is −1.3, indicating that the source is enriched mantle. The values of Rb/Cs, Ba/La, and La/Sm ratios suggest that subducting sediments formed an important component of the magmatic source. The presence of water-bearing minerals such as amphibole and biotite indicate a water-rich and oxygen-rich primitive magma system. Petrogenetic analysis indicates that the Akechukesai high-Mg diorites probably formed by melts and aqueous fluids produced from partial melting of the subducting sediments interacting with mantle peridotites. We hypothesize that, after the closure of the Proto-Tethys Ocean Basin in the Middle Silurian, the deep subducted slab broke-off and formed a slab window, asthenospheric material upwelled heating the subducting sediments and causing them to melt. Thus, we suggest that the emplacement of the Akechukesai high-Mg diorites mark the commencement of post-collisional magmatism. [ABSTRACT FROM AUTHOR]

When the Neo-Tethys subduction initiated has been a subject of debate, perhaps due to the lack of reliable evidence. This paper reports geochronological, geochemical, and Hf isotopic data for recently identified gabbro as well as diorite exposed in the Chanv area of the Gangdese in the southernmost margin of the western Lhasa block, western China. Zircon U–Pb dating indicates the Chanv magmatic rocks formed in two stages: latest Permian (gabbro, 254.8 ± 1.5 Ma) and Late Triassic (gabbro, 214.2 ± 2.0 Ma; diorite, 202.8 ± 1.1 Ma). Geochemical and Hf isotopic analyses reveal that the Chanv magmatic rocks of both stages have contrasting characters. The latest Permian gabbro has apparently higher TiO2 concentrations (> 3 wt.%) than the Late Triassic gabbro (0.86–1.24 wt.%). Although they all are enriched in light rare-earth elements (LREEs), the latest Permian gabbro displays no depletions in Nb and Ta, while the Late Triassic gabbro and diorite are apparently depleted in these two elements. In addition, the zircons from the latest Permian gabbro are all characterized by positive εHf(t) values whereas those from the Late Triassic gabbro dominantly by negative εHf(t) values. Conventional plots using multi-elements or elemental ratios all indicate the latest Permian gabbro has inherent resemblance to intraplate oceanic-island basalt (OIB) whereas the Late Triassic gabbro and diorite are of distinct arc affinity. Therefore, The Chanv latest Permian–Late Triassic magmatic rocks testify a switch of the tectonic environment in the southernmost Eurasian margin from latest Permian post-break-up to Late Triassic arc-related setting and thus constrain the initiation of the Neo-Tethys subduction between 255 Ma and 214 Ma. [ABSTRACT FROM AUTHOR]

This article presents new zircon U–Pb ages, data on whole‐rock major and trace elements for the Early Ordovician to Early Cretaceous granitic rocks exposed in the Mohe Basin of North‐east China, and reveals the tectonic evolution history of the Mohe area during this period. The zircon U–Pb dating results indicate that the magmatic activities from the Early Ordovician to Early Cretaceous in the Mohe area can be divided into six stages, which are ~473, ~281, ~247, ~215, ~130, and ~124 Ma, respectively. The granitic rocks mainly originated by partial melting of a depleted and heterogeneous lower crust, except for the quartz diorites at ~130 Ma, derived from the separated crystallization of mantle‐derived subalkaline basaltic magma. The rock associations and their geochemical features indicate that the granitic rocks of ~247 and ~215 Ma formed in an active continental margin setting, whereas the granitic rocks with formation ages of ~473, ~281, ~130, and ~124 Ma were formed in an extensional tectonic setting. Each stage of magmatic activity is consistent with the magmatism and tectonism of the Erguna Block. Based on the achievements of the previous studies, we put forward a comprehensive tectonic evolution of the Mohe area. From Early Ordovician to Late Permian (473 ~ 252 Ma), the Mohe area was influenced by the Palaeo‐Asian Ocean tectonic domain. Magmatism of Late Permian to Late Jurassic (247 ~ 155 Ma) is mainly due to the subduction of the Mongol–Okhotsk Ocean. During the Late Jurassic, the Erguna Block collided with the Siberian Craton and the southern margin of the Siberian Craton was uplifted and started furnishing sediments into the Mohe Basin. In the Early Cretaceous (~130 Ma), the Mohe area may have been controlled by the Palaeo‐Pacific Ocean and the Mongol–Okhotsk Ocean tectonic domains. [ABSTRACT FROM AUTHOR]

Several gabbro, gabbroic diorite, and diorite intrusions were emplaced in the Neotethyan Urumieh-Dokhtar magmatic arc in the Kahak area of the Zagros Orogen. The plutonic rocks intruded Cenozoic volcanic and pyroclastic succession. U-Pb dating via LA-ICP-MS of zircon yields early to middle Eocene ages of ~53 to 38 Ma for the diorite and gabbroic diorite in Veshnaveh and Naragh areas and Miocene ages of 23 to 20 Ma for gabbroic rocks in the Kerogan and Fordou areas. The Eocene magmatic phase occurred quite possibly as three continuous pulses. The Eocene and Miocene intrusions have negative Nb-Ta anomalies like those of subduction-related magmas. The Pb isotopic compositions show the involvement of subducted sediment in the source of the studied samples. The Eocene intrusions are tholeiitic and enriched in incompatible-trace-elements (especially the HFSE) compared to the Miocene intrusions which are calc-alkaline and have lower concentrations of most incompatible trace elements. Sr-Nd isotopic compositions of the Eocene rocks lie close to the mantle array and near Bulk Silicate Earth, but the Miocene suite is shifted to higher (87Sr/86Sr)i. The higher (87Sr/86Sr)i, along with larger Ba, K, Pb, and Sr anomalies, in the Miocene suite imply more slab fluid input and/or crustal contamination. Apparently, the Eocene mafic magmas formed in slightly metasomatized sub-continental lithospheric mantle (SCLM), whereas the Miocene suite was derived from highly metasomatized, deeper levels of the SCLM. We suggest that slab roll back occurred between the Eocene and Miocene and transferred the location of mantle partial melting to greater depths. [ABSTRACT FROM AUTHOR]

The Shiquanhe-Num Co ophiolitic mélange belt (SNOB) is one of two such belts along the Bangong-Nujiang suture zone (BNSZ) separating the Lhasa and Qiantang terranes of central Tibet. This study reports new geochronological, petrological and geochemical data for high-Mg dioritic dikes intruding the Shiquanhe ophiolitic peridotite. Based on LA-ICP-MS zircon U–Pb dating, dioritic dikes yield a Late Jurassic age of 162.8 ± 1.3 Ma. These are high-Mg diorites (53.0%–56.8% SiO2, 7.07%–8.82% MgO) with moderate TiO2 (0.95%–1.01%), high K2O+Na2O (6.02%–8.01%), and high contents of Cr (150–182 ppm), Ni (91–145 ppm) and Th (2.8–5.9 ppm). They are very similar to sanukites of the Setouchi volcanic rock belt (SW Japan). Shiquanhe diorites have high Sr/Y ratios (up to 41.3), distinct positive Pb anomalies, negative Nb anomalies and continental crust-like trace element patterns without negative Eu anomalies (average Eu/Eu* = 0.96). These geochemical characteristics indicate that Shiquanhe diorities were derived by partial melting of mantle peridotite as a result of interaction with hydrous melts of subducted sediments. Similar high-Mg magmas are common in the early evolution of a new subduction zone. Integrated with field observations and results from other studies of Late Jurassic high-Mg andesites and diorites along the SNOB, we argue that the Shiquanhe high-Mg diorites formed at an early stage of northward subduction of the Bangong-Nujiang Tethys ocean (BNO) beneath the Qiangtang terrane. Therefore, these results provide critical constraints on the Jurassic tectonic evolution of the Shiquanhe-Num Co ophiolitic mélange belt and are significant for understanding the evolution of the BNO. [ABSTRACT FROM AUTHOR]

• Cryogenian rift-related magmatism suggest early connection to the East Antarctic Shield. • Second extensional Cambrian magmatism might be linked to Gondwana final assemblage. • Heritage Group stratigraphy needs re-evaluation; could date back to Cryogenian. Our current understanding of the Ellsworth Mountains stratigraphy suggests the oldest sedimentary sequence (Heritage Group) was deposited in a Cambrian rift setting. This early Paleozoic age is then used as a key piercing point to help define Cambrian paleogeography for the southern paleo-Pacific margin of Gondwana, which places the Ellsworth Mountains between southern Africa and East Antarctica as part of West Gondwana. However, U-Pb zircon dating of a micro-diorite from the Heritage Group reveals a crystallization age of 682 ± 10 Ma, challenging chronostratigraphic and tectonic interpretations. Positive εHf t and mantle-like δ18O values for these Cryogenian zircons suggest that the rifting, affecting Mesoproterozoic crust, occurred during the Cryogenian rather than in the Cambrian. This finding strongly supports a connection between the Ellsworth-Whitmore Mountain crustal block and the Transantarctic Mountains in East Antarctica prior to the amalgamation of Gondwana. It also facilitates its contextualization during the breakup of Rodinia, likely positioned close to the Shackleton Range as a continuation of the Australia-Antarctic plate, which separated from Laurentia to form the proto-Pacific Ocean in the late Neoproterozoic. This connection is supported by the U-Pb, Hf, and O data in detrital zircon grains from the lowermost units of the Heritage Group, which indicate local, East Antarctic Shield, and probable Laurentian sources. A second magmatic event in the Cambrian (516 ± 7 Ma) is recorded through zircons from a basaltic andesite within the Liberty Hills Formation, which provides an absolute depositional age for this unit. This magmatism is linked to an extensional setting, albeit distinct from that of the Cryogenian micro-diorite. The Cambrian zircons yield elevated δ18O values, indicating a strong sedimentary influence on the magma source and crustal recycling. We interpret this Cambrian extensional magmatism as a result of a tectonic escape following the collision between the East Antarctic Shield and West Gondwana/Indo-Antarctic plates, leading to the formation of Gondwana. This interpretation argues against the hypothetical Pannotia supercontinent and the proposed Cambrian rift between this sector of the paleo-Pacific margin of Gondwana and southern Laurentia. [ABSTRACT FROM AUTHOR]

The Late Mesozoic tectonic evolution of the eastern North China Craton (NCC) remains controversial. In this study, a suite of Early Cretaceous mafic-intermediate dyke swarms found in the same section in the Jiaodong Peninsula, eastern NCC, were used to trace the nature of lithospheric mantle and crust–mantle interaction. Zircon U-Pb dating demonstrates that these dykes emplaced into the Jiaodong Peninsula during the same period (112–121 Ma). Diorite dykes have SiO2 contents of 52.7–54.1 wt.%, Na2O+K2O contents of 5.77–6.10 wt.%, a limited range of MgO (4.43–5.13 wt.%), Cr (64.8–85.5 ppm) and Ni (23.6–27.7 ppm), and a narrow range of (87Sr/86Sr)i isotopic ratios (0.709240–0.709246), ƐNd(t) values (−20.0 to −19.1) and ƐHf(t) values (ca. −23.9). Lamprophyre and dolerite dykes have low contents of SiO2 (50.5–55.4 wt.%) and Na2O+K2O (4.88–7.28 wt.%), high contents of Al2O3 (14.6–15.8 wt.%), MgO (5.83–8.60 wt.%), Cr (210–292 ppm) and Ni (114–149 ppm), and a narrow range (87Sr/86Sr)i isotopic ratios (0.709134–0.709788), ƐNd(t) values (−19.9 to −17.4) and ƐHf(t) values (−22.1 to −15.1). Both intermediate and mafic dykes exhibit strong large ion lithophile elements (LILE) enrichment and high field strength element (HFSE) depletion. These geochemical characteristics demonstrate that the magma was primarily derived from relatively low degrees of the partial melting of garnet-lherzolite mantle, which was modified by fluids from a subducting oceanic slab with marine sediments. Both the mafic dykes and intermediate dykes originated from the same magma source and formed in different stages of magma fractionation crystallization. The magma experienced the fractional crystallization of clinopyroxene and more ferromagnesian minerals in a hydrous condition, thus forming mafic dykes. Then, the residual calc-alkaline liquids upwelled into a low-H2O and low-pressure environment, in which more plagioclase crystallized from liquid, thus increasing the degree of differentiation and producing the Ca- and Al-rich diorite dyke. Combined with Late Mesozoic mantle-derived mafic-intermediate dykes and crust-derived volcanic rocks in the region, the eastern NCC has experienced considerable lithospheric thinning along with regional extensional tectonics, which was caused by the prolonged thermo-mechanical-chemical erosion on the lithosphere induced by the rollback of the subducted paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

The Archean Anshan Complex (AAC) in northeastern China is one of the best-preserved ca. 3.8 Ga outcrops worldwide, which are key to understanding the evolution of the early Earth. In this study, we carried out 1:10,000 geological mapping and integrated this with published whole-rock geochemical, zircon U–Pb age, and O–Nd–Hf–W isotopic data, along with new zircon U–Pb and Si–O isotopic data. We used these data to establish a geochronological framework for the AAC and investigate its origins and tectonic setting, and differentiation of the early Earth. Our new mapping shows that the AAC can be divided into several rock associations based on the zircon U–Pb ages and lithologies: (1) Eoarchean (ca. 3.8 Ga) trondhjemitic gneiss and meta-quartz diorite; (2) Paleoarchean (ca. 3.3 Ga) gneiss and migmatite; (3) Mesoarchean (ca. 3.1 Ga) granitic gneiss; (4) Mesoarchean (ca. 3.0 Ga) monzogranite; (5) Neoarchean (ca. 2.5 Ga) K-rich granite; and (6) Archean supracrustal rock. The ca. 3.8 Ga rocks are exclusively exposed as enclaves within the ca. 3.3 Ga gneiss and migmatite unit at Dongshan, Guodishan, Shengousi, and Hujiamiao. Some ca. 3.8 Ga components at Baijiafen and Dongshan cannot be visually identified due to strong deformation and migmatization. The ca. 3.8 Ga Anshan trondhjemitic gneiss and meta-quartz diorite have coupled heavy Si–O isotopic compositions, indicative of the involvement of supracrustal silicified materials in their sources. (La/Yb) N ratios vary widely in the different ca. 3.8 Ga rock types (i.e., 9–53 for the trondhjemitic gneisses and 3–8 for the meta-quartz diorites), indicating they formed at different pressures. We suggest the ca. 3.8 Ga trondhjemitic gneisses were derived by partial melting of a subducted slab, and the 3.8 Ga meta-quartz diorites might have been derived by partial melting of a mantle wedge that had been metasomatized by fluids released from the subducted slab. Highly variable ε Nd (t) (−4.5 to +10.1) and ε Hf (t) (−3.8 to +6.1) values of the ca. 3.8 Ga rocks indicate that their protoliths involved at least two end-member components that were derived from enriched and ultra-depleted mantle reservoirs. Finally, the 182W excess (μ182W = +8.3 to +12.9) of the ca. 3.8 Ga rocks might be due to either early mantle differentiation or a lack of late accreted materials. However, 142Nd isotopes (μ142Nd = +1.8 to +9.2) of these ca. 3.8 Ga rocks do reveal a differentiation event in the early Earth that produced two end-member reservoirs with positive and negative μ142Nd anomalies. We conclude that plate tectonics likely had an important role in the onset of continental nuclei in North China at ca. 3.8 Ga, and the precursors of these oldest rocks can be used to decipher multiple mantle–crust differentiation events during 4.5–3.8 Ga. [ABSTRACT FROM AUTHOR]

The Yinshan Block constitutes the northwestern segment of the North China Craton. We characterized the geochemistry, zircon U–Pb geochronology, and Hf isotopic composition of a diorite pluton in the Yinshan Block. The zircon U–Pb data yield a protolith formation age of 2535 ± 8 Ma (MSWD = 0.46), followed by recrystallization at 2465 ± 14 Ma or 2431 ± 30 Ma; the granite vein which intruded into the diorite pluton gives a formation age of 2453 ± 5 Ma (MSWD = 1.6), according with the recrystallization age of the diorite. These diorites are characterized by moderate Mg# value and MgO, Cr, and Ni content and have relatively low Sr/Y and (La/Yb)N ratios and slightly Eu anomalies and are enriched in LILEs and depletion in high field strength elements. High‐Sr + Ba granites with low K2O/Na2O characteristics are also shown by these diorites, and the εHf(t) of zircons lie between +1.3 and −7.2, imply these diorites are most likely derived from partial melting of a thickened lower crust with minor involvement of enriched mantle. These geochemical and isotopic characteristics suggest the diorite magmas derived from an accreted arc‐related rocks remelting in a low‐pressure environment along the continent margin. Hereby, we propose a supplement to the model of crustal growth and evolution in the Yinshan Block, involving subduction and collision in the Neoarchean. [ABSTRACT FROM AUTHOR]

The Saveh magmatic complex is a composite intrusion of diorite to tonalite. It is part of the Urumieh-Dokhtar magmatic arc in central Iran. Zircon U Pb dating indicates that emplacement and cooling occurred 37–40 Ma ago in late Eocene (Bartonian) time. Saveh igneous rocks define a continuous mafic-felsic continuum in terms of SiO 2 (55.4–70.8 wt%), Al 2 O 3 (14.2–19.8 wt%) and CaO (6.4–17.1 wt%) contents. The initial values of 87 Sr/ 86 Sr and ɛ Nd (t) are 0.7048 to 0.7062 and + 2.6 to +3.4 (Mean = +2.9). Nd model ages (T DM  = 555 to 616 Ma) are consistent with derivation from Iranian continental crust and subcontinental lithospheric mantle of Cadomian age (500–600 Ma). Saveh igneous rocks are enriched in K, Cs and Pb and depleted in P, Nb and Ta, indicating that the magma source was moderately affected by slab-derived fluids, as expected for the Eocene tectonic environment. The continuum of rock types from diorite to graphic eutectic tonalite indicates that magmatic evolution was controlled by the F (FeO + MgO + MnO)-Anorthite (An)-Orthoclase (Or) cotectic with minor contamination by supra-crustal components. Similar initial ratios of 87 Sr/ 86 Sr and 143 Nd/ 144 Nd for all of the rocks and the slightly younger age of tonalitic rocks (2–3 Ma younger) further indicate that the crystallization of quartz and plagioclase with graphic texture occurred in the final stage of magmatic differentiation. Saveh magmas reflected partial melting of Iranian subcontinental lithospheric mantle due to extension above the Neo-Tethys subduction zone. [ABSTRACT FROM AUTHOR]

The Shihu gold deposit, located in the middle-south section of the core of the Fuping mantle branch structure, is hosted in the Archean Fuping Group and adjacent to the quartz diorite porphyrite. The gold deposit is the only large gold deposit with reserves of more than 30 tons gold discovered in western Hebei Province so far. In order to constrain the timing of mineralization of this ore deposit, this paper focuses on the isotopic dating of zircon and pyrite. Zircons in gold-bearing quartz veins are magmatic in origin and no hydrothermal zircon has been found in such quartz veins, indicating that zircons were derived from the wall rocks. U-Pb ages of zircons fall mainly in the two domains: 2492 ± 82 and 136 ± 4 Ma, respectively, indicative of the contribution of the Fuping-Group TTG gneiss and Yanshanian igneous rocks, respectively. The Re-Os isotopic compositions of pyrites in the gold-bearing quartz veins yield an isochron age of 127 ± 31 Ma. Combined with other dating results, we suggest that the main metallogenic age of the Shihu gold deposit is 120-127 Ma. [ABSTRACT FROM AUTHOR]

• The granodiorites and monzonitic diorites were originated from slab melts and slab melts-metasomatized mantle source, respectively. • The alkali feldspar granites were produced by partial melting of a crustal source in an extension background. • The gabrros were generated by partial melting of mantle wedge metasomatized by slab-derived fluids. • A slab window was likely happened at 2.46–2.44 Ga in the south margin of the Yinshan Block. The earliest Paleoproterozoic magmatic rocks have recorded the transition from the Neoarchean cratonization of the NCC to its post-Archean tectonic evolution, which will provide insight into the onset of the modern-style subduction. This study focuses on the early Paleoproterozoic granodiorite, monzonitic diorite, alkali feldspar granite and gabbro in the Guyang area to decipher the early Paleoproterozoic tectonic evolution of the Yinshan Block. Zircon U–Pb dating indicates that these rocks were emplaced at ca 2.46 – 2.41 Ga. The ∼ 2.46 Ga granodiorite samples have high Sr contents, low Y and Yb contents with high Sr/Y ratios, similar to the characteristics of adakitic rocks. Based on their high Mg# values, Na 2 O/K 2 O ratios, Cr, Co and Ni concentrations, and positive ε Nd (t) values, we propose that the granodiorite was likely produced by partial melting of subducting oceanic slab. The contemporary monzonitic diorite samples are characterized by high Nb concentration, which are similar to those of Nb-enriched basalt/andesite. The monzonitic diorite samples are characterized by LREE-enriched patterns with negative Eu anomalies and have negative ε Nd (t) values (-0.4 – −1.4), which suggest that they were derived from partial melting of fertile mantle peridotite metasomatized by adakitic melts. The ∼ 2.44 Ga alkali feldspar granite samples have negative ε Nd (t) values (-4.0 – −1.9) and show geochemical characteristics of A-type granites, indicating an extension background. The distinct geochemical characteristics of ca. 2.46 – 2.44 Ga Guyang adakatic granodiorite, Nb-enriched monzonic diorite and A-type alkali feldspar granite suggest that a slab window was opened in the southern margin of the Yinshan Block. The gabbros were emplaced at ∼ 2.41 Ga revealed by U-Pb dating. The enriched LREEs and relatively flat HREEs patterns with negative Nb-Ta anomalies of gabbros indicate a subducting tectonic setting. Their high Ba/Th and low Nb/Y ratios imply that the mantle source was metasomatized by slab-derived fluids. This special rock association not only constrains the tectonic evolution in the southern margin of the Yinshan Block, but also indicates modern-style subduction operated already in the early Paleoproterozoic. [ABSTRACT FROM AUTHOR]

The Hamutenha intrusion (Huíla province, SW Angola) is a 3-km-long elongated magmatic body defined by a set of two intrusive units. The northern unit is formed by alternating bands of dunites and olivine gabbros, while the southern unit is composed of amphibole diorites. The Hamutenha body is hosted by the Paleoproterozoic Epupa Complex in the Angolan Shield, SW margin of the Congo Craton. A mineralogical, petrological and geochemical study of the Hamutenha intrusion has been performed. The constrained compositional features of the parental melt suggest interaction of tholeiitic magmas with a significant enrichment in Fe and Ti. Although disseminated Fe–Ni–Cu-(Co) secondary sulphides are observed, both the crustal contamination parameters and generally low bulk-rock metals contents indicate that these elements were most likely previously extracted from the parental melt. U–Pb zircon dating of amphibole diorite samples from the southern unit yields a date of 1844 ± 14 Ma. These data suggest that the emplacement of these rocks was previous to the KC emplacement and it was probably related to the Paleoproterozoic Epupa Complex magmatism. • Hamutenha is a 3-km-long magmatic banded body composed of two different units that potentially hosts magmatic sulphide mineralisations. • Its parental melt was an evolved basaltic tholeiitic magma significantly enriched in Fe and Ti. • U–Pb zircon dating from the Hamutenha southern unit yields 1844 ± 14 Ma and 1774 ± 20 Ma ages, recording the Epupa Complex Paleoproterozoic magmatism. [ABSTRACT FROM AUTHOR]

We report zircon U–Pb age data, Hf isotopes, and bulk-rock geochemical data for the Middle to Late Triassic granitoids in the Taerqi-Chabaqi-Kutihe region within the Xing’an Block of the central Great Xing’an Range, northeast China. Euhedral to subhedral zircon grains were extracted from the nine representative granitoids. These zircons exhibit oscillatory zoning typical of a magmatic origin. The zircon U–Pb determinations on the monzogranite, syenogranite and quartz diorite samples yielded ages between 244 Ma and 206 Ma, which essentially suggests that the magmatism in the Xing’an Block occurred during the Middle to Late Triassic period. Geochemically, these granitoids have SiO 2 = 62.97–76.31 wt%, A/CNK = 1.03–1.51, and K 2 O/Na 2 O = 0.40–2.39, we infer that they belong to high-K calc-alkaline series and are peraluminous I-type granites in nature. The major and trace element systematics indicate that these granitoids have different origins. Among them, the 244 Ma syenogranite of Taerqi and the 230–206 Ma monzogranite and syenogranite of Kutihe were probably generated from partial melting of pre-existing juvenile arc-type rocks in a relatively shallow crustal level. The 210 Ma quartz diorite of Chabaqi likely originated from the hybridization between a depleted mantle component and the juvenile subducted oceanic crustal materials that were buried to depths of the middle to lower continental crust. The 212 Ma monzogranite and syenogranite of Kutihe were probably generated from the partial melting of miscellaneous lower crustal materials at high pressure conditions. By combining these new data with regional geological data, we conclude that the early Mesozoic evolution of the central Great Xing’an Range was governed by two superimposed tectonic regimes, i.e., (1) post-orogenic extension due to slab break-off after the closure of the Paleo-Asian oceanic basin along the Hegenshan-Heihe suture belt, and (2) back-arc extension associated with the southward subduction of Mongol-Okhotsk oceanic plate. [ABSTRACT FROM AUTHOR]

LA-ICPMS zircon U-Pb dating has been greatly advanced and widely applied in the past decade because it is a cheap and fast technique. The internal error of LA-ICPMS zircon U-Pb dating can be better than 1%, but reproducibility (accuracy) is relatively poor. In in order to quantitatively assess the accuracy of this technique, zircons from two dioritic rocks, a Mesozoic dioritic microgranular enclave (FS06) and a Neoproterozoic diorite (WC09-32), were dated independently in eight laboratories using SIMS and LA-ICPMS. Results of three SIMS analyses on FS06 and WC09-2 are indistinguishable within error and give a best estimate of the crystallization age of 132.2 and 760.5 Ma (reproducibility is ∼1%, 2RSD), respectively. Zircon U-Pb ages determined by LA-ICPMS in six laboratories vary from 128.3±1.0 to 135.0±0.9 Ma (2SE) for FS06 and from 742.9±3.1 to 777.8±4.7 Ma (2SE) for WC09-32, suggesting a reproducibility of ∼4% (2RSD). Uncertainty produced during LA-ICPMS zircon U-Pb analyses comes from multiple sources, including uncertainty in the isotopic ratio measurements, uncertainty in the fractionation factor calculation using an external standard, uncertainty in the age determination as a result of common lead correction, age uncertainty of the external standards and uncertainty in the data reduction. Result of our study suggests that the uncertainty of LA-ICPMS zircon U-Pb dating is approximately 4% (2RSD). The uncertainty in age determination must be considered in order to interpret LA-ICPMS zircon U-Pb data rationally. [ABSTRACT FROM AUTHOR]

The Middledale Gabbroic Diorite (MGD) in New South Wales, Australia, is host to the internationally distributed TEMORA 2 zircon reference material and its prototype, TEMORA 1. The original characterisation of the source of the reference zircons revealed that the more altered TEMORA 2 host rock contains an order of magnitude more zircon than the TEMORA 1 host, despite similar bulk-rock Zr concentrations. Although TEMORA 1 and 2 preserve the same U–Pb age, they are variable in oxygen isotope composition. In this study, petrographic observations in concert with bulk-rock and mineral geochemistry and zircon U–Pb geochronology have been applied to new samples of the MGD to investigate the link between alteration and zircon abundance. Trace element maps reveal that the products of late-stage, deuteric alteration (particularly actinolite after hornblende) are depleted in Zr, and many other trace elements, relative to the unaltered mafic, magmatic phases. It is posited that the conversion of hornblende to secondary amphiboles in the latter stages of magma solidification liberated Zr, permitting the crystallisation of additional zircon. New high resolution SIMS U–Pb determinations on four samples confirm the age homogeneity of the zircon across the pluton and reaffirm the value of TEMORA 2 as a valuable geochronological reference material. Zircon oxygen isotope data have been acquired for these same samples and the mean δ 18 O values encompass the accepted values for TEMORA 1 and 2. Likewise, the Hf-isotope determinations are similar to the accepted TEMORA 2 composition. Together with petrographic observations, these data reveal the TEMORA 2 zircon and its host to be broadly reflective of the relatively coarse-grained portions of the MGD, and that the isotopically less evolved compositions ( i.e. the lower δ 18 O of TEMORA 1 and low δ 18 O, high 176 Hf/ 177 Hf of one sample from this study) are associated with a relatively fine-grained, marginal lithology. Given δ 18 O values greater than typical mantle-derived zircon and the broad correlation between O- and Hf-isotopic compositions, the data imply the pluton evolved by crustal contamination of a primitive magma. [ABSTRACT FROM AUTHOR]

The article discusses mineralization of Voznesenskoe copper–porphyry deposit in the Main Uralian Fault Zone in Russia. Topics discussed include parental rocks' composition, research on composition of plagiogranite–porphyries, and Uranium–lead (U–Pb) dating of zircons. Other topics include use of Samarium-neodymium (Sm-Nd) dating method and composition of gabbro diorites from the Karagaikul ore.

Dioritic--trondhjemitic gneisses of Neoarchean age are widely distributed throughout the Gualanyu--Shangying area in Eastern Hebei, North China Craton. These orthogneisses consist of dioritic, trondhjemitic, and quartz-rich trondhjemitic gneisses, which were subjected to amphibolite- to granulite-facies metamorphism. LA-ICP-MS zircon U--Pb isotopic dating reveals that the magmatic precursors of these rocks were contemporaneously emplaced from 2535 ± 23 to 2513 ± 8 Ma, reflecting an important Neoarchean dioritic--trondhjemitic magmatic event followed by sequential Proterozoic tectonothermal events between 2472 ± 60 and 2307 ± 50 Ma. Dioritic and trondhjemitic gneisses exhibit similar zircon ɛHf(t) values of +1.5 to +5.2 and +2.9 to +5.3, respectively, indicating their depleted mantle affinity. Geochemical analysis reveals that the dioritic gneisses have low SiO2 contents (55.4-63.0%), various MgO contents (2.07-4.78%) and Mg# (36.07-63.56), and high (La/Yb)N ratios (5.45-15.19). In contrast, the trondhjemitic gneisses exhibit higher SiO2 contents (67.4-73.8%) and (La/Yb)N ratios (12.86-76.73), and lower MgO contents (0.66-2.67%), although their Mg# (36.29-61.41) are similar to those of dioritic gneisses. These geochemical and zircon Lu--Hf isotopic features, together with geochemical modeling, suggest that the dioritic magmas were derived mainly from the partial melting of a depleted mantle wedge that was metasomatized by slab-derived melts or fluids, and that the trondhjemitic magmas were formed by fractional crystallization of the dioritic magmas. Quartz-rich trondhjemitic gneisses exhibit extremely high SiO2 contents (77.4-84.6%) with zircon ɛHf(t) values ranging from -3.4 to +4.1, suggesting that their precursors formed after the partial melting of a mixed magmatic source. It is suggested that the precursors comprised a mafic member derived from a mantle wedge altered by oceanic slab melts or fluids, and a felsic member derived from the partial melting of ancient crustal material. These new data, combined with previous studies of contemporaneous metavolcanic rocks in Gualanyu-Shangying area and surrounding areas, suggest that the magmatic precursors of these Neoarchean dioritic--trondhjemitic gneisses formed in a subduction-related tectonic environment at an E-W strike convergent plate margin. Furthermore, the Eastern Block of the North China Craton had a major lateral accretion of crustal growth in the north margin in the Neoarchean, whereas vertical crustal growth and recycling under plume tectonic backgrounds occurred in the interior of the Eastern Block. [ABSTRACT FROM AUTHOR]

Ar-Ar, Sm-Nd, U-Pb, and Lu-Hf isotope data are reported on the gabbro of the Volkovsky Massif, the only massif of the Uralian Platinum Belt wherein economic copper-iron-vanadium and high-grade gold-palladium mineralization is present. The massif is made up of gabbro blocks with concentrically zoned structure and diorite intrusions in its core. In the northeast and southwest, the gabbro is cut by syenite of the Kushva Massif. Gabbro blocks mainly consist of the olivine-anorthite gabbro, while labradorite two- pyroxene gabbro intersects both olivine-anorthite gabbro and Ti-magnetite and copper-PGE mineralization developed in them. The study of both gabbro types by Sm-Nd isochron and U-Pb (SHRIMP II) zircon methods with subsequent REE and Lu-Hf isotope analysis of zircon made it possible to date reliably (428 ± 7 Ma (SHRIMP) and 436 ± 21 Ma (Sm-Nd)) postore labradorite gabbro and, correspondingly, the upper age limit of the mineralization of the Volkovsky Massif. Ore-bearing olivine-anorthite gabbro contain four different-age zircon populations: 2682 ± 37-972 ± 18 Ma, 655 ± 15 to 565 ± 9 Ma; 450 ± 12 Ma, and 343 ± 8 Ma. Hf-Nd isotope systematics showed that zircon with an age of 450 ± 12 Ma presumably marks the formation age of the rocks, the older zircon was trapped, while zircon with an age of 343 ± 8 Ma was formed during low-temperature transformation of the rock and sometimes contains excess radiogenic Hf. Proterozoic xenogenic zircon was inherited from diverse rocks of ancient crust, while the oldest grain with an age of 2065 Ma was possibly formed in a deep mantle source. Vendian zircon was presumably also entrapped, and its morphology and geochemistry point to the crystallization from a basaltic melt. The abundance of pre-Paleozoic zircon in the olivine-anorthite gabbro suggests significant contribution of ancient material in their petrogenesis. This material could serve as source of ore components (metals and sulfur) for unique copper-sulfide gold-PGE mineralization of the Volkovsky Massif. [ABSTRACT FROM AUTHOR]

The Early Miocene Marshenan intrusion, in the central part of the Urumieh-Dokhtar magmatic arc (UDMA), central Iran, includes granodiorite-granite and diorite; it is a classic example of a Cu Au barren intrusive system. Zircon U-Pb dating indicates that the diorite display an age of 20.32 ± 0.36 Ma, coeval with granodiorite rocks (20.5 ± 0.8 Ma). These rocks are composed of feldspar, quartz, amphibole, biotite, titanite, and magnetite. In the granodiorites, the plagioclase composition ranges from oligoclase to bytownite, the amphiboles are magnesio-hornblende and biotites is Mg rich, related to calc-alkaline orogenic suites in the region. Plagioclase phenocrysts exhibits oscillatory zoning and marked changes in the abundance of elements, such as Ba, Sr, and Fe, suggesting magma mixing/mingling may have had a role in generating these parental magmas. The average calculated P–T conditions of the granodiorite and diorite rocks are about 730 °C and 2.1 kbar and 733 °C and 1.7 kbar, respectively, corresponding to near solidus conditions equal to emplacement depths of ~7 to 8 km. Magmatic H 2 O contents and ƒO 2 calculated from crystallized amphiboles indicate that the Marshenan granodiorite had initial magmatic H 2 O contents ~5 wt% and relatively high ƒO 2 (ΔNNO; ave. 1.3) and the diorite had initial magmatic H 2 O contents ~4.7 wt% and relatively high ƒO 2 (ΔNNO; ave. 1.5), both consistent with the presence of phases, such as hornblende, biotite, magnetite, and titanite. In comparison with other intrusions in the UDMA, the Marshenan intrusion formed via the same physico-chemical mechanisms like other barren intrusions, whereas the fertile intrusions exhibit slightly higher temperatures, pressures, ƒO 2 , and H 2 O values than the barren intrusions. These compiled data suggest that, in spite of the high magmatic H 2 O and ƒO 2 contents, the Marshenan and other barren intrusions in the UDMA will not produce porphyry Cu mineralization, unlike the giant Kerman deposit, probably due to magma source, magmatic evolution processes, timing of volatile exsolution, pre-existing crustal-scale fractures, coeval volcanism, and extended duration of volatile saturated crystallization to subsolidus conditions. [ABSTRACT FROM AUTHOR]

High-grade terranes showing multiple episodes of leucogranite magmatism are ideal to assess the fertility of crustal protoliths. Two episodes of Paleoproterozoic leucogranite magmatism occur in the Mahalapye Complex high-grade terrane, at the northern edge of the Kaapvaal Craton. The older one (leucogranite 1) at ∼2.05 Ga represented by leucosomes, thin veins and dykes is related to the melting of ∼2.06 Ga biotite-bearing diorite gneiss. In comparison, the younger episode (leucogranite 2) at ∼2.03 Ga forms massive bodies. Leucogranite 1 is associated with the migmatitic diorite gneiss and crosscut by the ∼2.04 Ga granodiorite. Leucogranite 2 contains xenoliths of diorite gneiss and granodiorite, as well as inclusions of quartz-poor and quartz-rich metapelites (Bt + Crd + Pl + Kfs + Spl ± Sil ± Grt + Ilm + Qz). Phase equilibria modelling of a representative quartz-poor metapelite indicate that its partial melting occurred at ∼810 °C and ∼4.8 kbar in the presence of aqueous fluid. The peraluminous, ferroan and alkalic composition of the predicted melt is comparable to the chemistry of leucogranite 2. The larger volume of anatectic melt for the estimated P-T condition corresponds to the occurrence of leucogranite 2 as massive bodies. The lower temperature of in-situ anatexis (<750 °C) at a deeper level (∼7.3 kbar) and lack of additional fluid, likely did not generate significant melt fraction during the formation of leucogranite 1. The contrast in the fertility of the two protoliths with respect to production of leucogranite melts was also related to different setting of melting. Melting of diorite gneiss is related to the local influence of mafic dykes and sills, whereas melting of metapelite is related to regional collision. It follows that high pressures, water-deficient regimes and localized heat sources produce limited volumes of partial melt, whereas high temperatures, fluid-present regimes and a large-scale heat source produces higher volumes of melts. [Display omitted] • Two episodes of leucogranite (LG1, LG2) magmatism in the Mahalapye Complex. • Dehydration melting of diorite gneiss (∼730 °C/∼7.2–7.5 kbar) formed the less dominant LG1. • Fluid-present melting of metapelite (∼810 °C/∼4.8 kbar) formed the dominant LG2. • Phase equilibria modelling indicates large content of anatectic melt for LG2 than LG1. • Temperature, presence/absence of fluid, scale of heat source, affect fertility of protoliths. [ABSTRACT FROM AUTHOR]

The Variscan basement within the Western Carpathian Alpine architecture generally consists of metaluminous/peraluminous tonalite/granodiorite massifs and high-grade metamorphic complexes of metapelites, metaultramafites, and metabasites with relics of eclogites. Unfortunately, the Variscan crystalline basement of the Western Carpathians is only fragmentally exposed. Therefore, the proposed geodynamic evolutionary model for the Variscan granites of the Western Carpathians is primarily based on granite data from the Malá Fatra Mts. with additional dating from the High Tatra Mts. The oldest magmatic age of 362 ± 4 Ma in the Malá Fatra horst was recorded in diatexites from a high-grade metamorphic complex, which is related to crustal anatexis during Variscan subduction. Subsequent collisional event and break-off of the subducted slab promoted exhumation of the diatexites within the high grade metamorphic complex and intrusion of 353 ± 3 Ma old Tournaisian tonalite. Intensive heat input after slab break-off from the rising asthenosphere generated melting of the lower crust and extensive calc-alkaline, Mg-rich granitic magmatism in a short time span from 347 ± 4 to 342 ± 3 Ma. These Visean granitic rocks caused thermal overprint on the roof metamorphic rocks, including diatexites and Tournaisian tonalites at ca. 348 ± 5.6 to 342 ± 3 Ma. The Visean granite formation was controlled by the mixing of hot magmas, which is indicated by the presence of composite oligoclase/andesine plagioclase with preserved labradorite cores, alkali feldspars with Na 2 O ≥ 2 wt%, zoned apatite, the presence of antiperthite, and quartz ocelli. Elevated contents of mantle-derived elements like V, Ni, Cr, Ba, high Sr/Y ratio of ~44, steep LREE and flat HREE segments of chondrite-normalised patterns document adakite-like feature of the investigated granitic rocks which resulted from melting of a mixed lower-crustal and mantle sources and crystallisation in the presence of garnet. Unusual abundance of Fe–Ti oxides in granodiorites with magmatic cooling temperatures of 735–756 °C supports high-T input from mantle. In the High Tatra Mts., diorite xenolith shows the age of 359.2 ± 3 Ma, and its host granodiorite the age of 350.1 ± 2.6 Ma. The diorite contains acicular zircons, which points to rapid exhumation. Stubby zircon of the host granodiorite shows regular, oscillatory zoning controlled by a gradual temperature decrease. The non-comagmatic relationships between diorite and host granodiorite are indicated also by a difference in zircon Th/U ratio, which is 0.2 for the host granodiorite, but 1.0 for the diorite on average. The presented data show that slab break-off could have been a mechanism that promoted Variscan granitic magmatism in the Western Carpathians. • Variscan subduction, slab break-off, exhumation and partial melting recorded in the Western Carpathians • Famennian (365-359 Ma), Tournaisian (359-353 Ma), and Visean (348–342 Ma) granitic magmatism recognised • Visean granites with adakitic signature derived from the melting of a mixed lower-crustal and mantle sources [ABSTRACT FROM AUTHOR]

[Display omitted] • Summaries of Mesozoic intrusions and related Cu-Au deposits in Tongling, eastern China. • Tongling region experienced two stages of magmatic activities corresponding to compressional and extensional settings. • Two stages of magmatism and mineralization are closely related to the subduction of the Paleo-Pacific plate. • Ore-forming fluids mainly come from magma and are mixed with a small amount of meteoric water. The Tongling ore-cluster region is one of the most important Cu-Au polymetallic producers in the famous Lower Yangtze River Metallogenic Belt (LYRMB) in eastern China. The Cu-Au polymetallic ore deposits can be divided into four types, i.e., skarn, strata-bound hydrothermal, porphyry, and cryptobreccia, closely related to the Late Jurassic to Early Cretaceous magmatism. We summarize the geology of the Mesozoic Cu-Au deposits in Tongling, eastern China, and revisit the age distributions and geochemical characteristics of associated Mesozoic intrusions, by integrating a large number of published geochemical data (including major and trace elements for both early-stage and late-stage intrusions, whole-rock Sr-Nd-Pb isotopes, and zircon U-Pb age and Hf isotopes for early-stage intrusions), to reveal their sources and genesis. According to the U-Pb ages of intrusions, the main magmatic events in the area can be divided into two stages, i.e., 152–135 Ma and 135–124 Ma, respectively. The early-stage magmatism mainly produced Cu-Au mineralization-related dioritic intrusions, including pyroxene diorite-pyroxene monzodiorite, quartz diorite-quartz monzodiorite, and granodiorite, showing unobvious geochronological order. Geochemical data of Late Jurassic-Early Cretaceous intrusions from the early-stage magmatism suggest that they are all derived from a similar source composed of different proportions of slab-derived melt, metasomatized lithospheric mantle, and a lesser content of lower crust materials. Among them, the key differences lie in that more lower crust materials are incorporated in the source of intermediate-felsic rocks compared to intermediate-basic rocks. The late-stage magmatism produced a wide variety of rocks (diorite porphyry, syenite porphyry, granite porphyry, monzonite, and granite porphyry), which are related to Pb-Zn deposits. The late-stage igneous rocks may evolve from the early-stage rocks and have experienced fractional crystallization of apatite, ilmenite, and other minerals. Both early and late-stage magmatic events in the Tongling region were formed in the subduction setting, and corresponding to compression and extensional setting, respectively. Besides, the H-O isotopes of different kinds of minerals suggest that the ore-forming fluids of most ore deposits were mainly derived from the magma and mixed with a small amount of meteoric water in the late-stage mineralization. The S isotopes of sulfides show that the ore-forming materials come from the magma, accompanied by the addition of original sediments. [ABSTRACT FROM AUTHOR]

The Gangdese magmatic belt, which formed by Mesozoic northward subduction of Neo-Tethyan oceanic lithosphere and Early Mesozoic India-Asia collision, is an excellent natural laboratory for study of subducting slabs, crustal growth, the reworking of convergent continental margins and interaction of crust-mantle in general. Although many studies have examined this belt, the petrogenesis of arc magmas and the geodynamic architecture of the subducting slab are still contentious. Discoveries of igneous rock exposures are important in reconstructing the tectonic regime and evolution of southern Tibet, and provide new constraints on unresolved issues. Here we report two newly identified intermediate rocks, shedding new light on both the formation of arc-type magmas, and the tectonic evolution of the Neo-Tethys during the Late Mesozoic. Zircon SHRIMP II U-Pb dating indicates that a Late Cretaceous gabbro diorite pluton formed at 90.3 ± 1.4 Ma, and a Late Jurassic diorite porphyry pluton crystallized at 157.9 ± 2.3 Ma. The former has positive zircon ε Hf (t) values of 8.03–10.86 and whole-rock ε Nd (t) values of 4.11–4.37, with δ18O zircon values of 5.84‰–6.70‰, slightly above the values of mantle zircon (5.3‰ ± 0.6‰). The latter also has positive zircon ε Hf (t) (10.29–12.77) and whole-rock ε Nd (t) (5.54–5.78) values, with normal mantle-like zircon δ18O values of 5.19‰ to 6.00‰. All samples of both plutons display arc-type signatures characterized by enrichment in light rare earth elements (LREEs) and depletion in high field strength elements (HFSEs) (e.g., Nb, Ta, Ti and P). Based on multiple isotopic (Sr–Nd–Hf–O) and whole-rock geochemical characteristics, we conclude that the Late Cretaceous gabbro diorite was derived from partial melting of depleted mantle that had been metasomatized by subducted-sediment-derived melts (~5 vol%). The Late Jurassic diorite porphyry is inferred to be a product of fractional crystallization of primary andesitic magmas with limited contents of Fe-Ti oxide and amphibole, and minor plagioclase accumulation. Pelagic sediments and enriched materials were a negligible component of the precursor magmas of the diorite porphyry, relative to the gabbro diorite pluton. Considering the temporospatial distribution of igneous rocks over the whole Gangdese magmatic belt, we suggest that Late Jurassic magmatism was related to normal angle subduction of the Yarlung Tsangpo Neo-Tethyan oceanic lithosphere, and early Late Cretaceous magmatism was triggered by rollback of the Neo-Tethyan oceanic slab. • Identification of Late Jurassic magmatism for the first time in the Dazhuka region. • Sediments-derived melts played a key role in the formation of the diorites. • The Late Jurassic magmatism was related to northward subduction of the Neo-Tethys. • Diorites formed by partial melting of depleted mantle. [ABSTRACT FROM AUTHOR]

Tertiary granitoid rocks including diorite, quartz diorite, quartz monzodiorite, monzonite, and quartz monzonite occur in southeast of Qom and to the east of Bidhand fault in the central Urumieh-Dokhtar Magmatic Arc (UDMA). Zircon U–Pb dating reveals an age of ca. 17 Ma for the crystallization of Kerogan quartz diorite. The study samples show sub-alkaline to transitional, metaluminous, and I-type affinity with low to middle SiO 2 (53.9–63.9 wt%). Micro granitoid enclaves (MGEs) are widespread in these rocks, exhibiting diorite to monzodiorite composition (SiO 2 = 56.75–58.4 wt%). MGEs and host rocks are slightly enriched in LREEs and LILEs, and depleted in HFSE including Nb, Ta and Ti as expected in granitoids formed in an active continental margin setting. The granitoid rocks display initial Sr isotopic compositions of 0.7047–0.7062, positive ε Nd (t) of 3.2–6.6, and 206Pb/204Pb (18.6431–18.8499), 207Pb/204Pb (15.6322–15. 6902), and 208Pb/204Pb ratios (38.5585–38.9325), and positive zircon ε Hf (t) values of 6.7–8.7. MGEs also display identical Sr-Nd isotopic compositions (87Sr/86Sr i = 0.70537–0.70576; ε Nd (t) = 2.3–5.3) to the host rocks. The isotopic characteristics in combination with the geochemical signatures indicate that the granitoid rocks and MGEs most likely originated by interaction between mantle-derived mafic and basaltic lower crust-derived melts. Major and trace element modeling reveals that the mafic lower crust is composed of less ~40% partial melting of garnet-free amphibolite. Petrographic and geochemical characterization together with bulk rock Nd-Sr isotopic data suggest that host rocks and associated enclaves derived from the same parent by interaction between basaltic lower crust (~10%) and lithospheric mantle (~90%) during their generation that subduction related compositions have also been involved in their petrogenesis. This magma has experienced high fractional crystallization but minor crustal contamination during magma ascent to the upper crustal level. Petrographical, geochemical, and Sr-Nd-Pb isotopic similarities between granitoid and MGEs imply that MGEs are cognate late cumulates, formed by pressure quenching mechanism during the late stage of magma evolution in crustal magma chamber. The Tertiary magmatism in the study area originated in an arc-related setting induced by slab roll-back of northward Neo-Tethyan oceanic lithosphere subduction beneath central Iranian micro continent and resulted in lithospheric extensional regime and subsequently asthenosphere upwelling. The heat induced by the upwelling of the asthenosphere likely led to melting of upper mantle and the mafic crustal material during Early Miocene as the final magmatism phase in the central part of the UDMA before collision. [Display omitted] • Bidhand granitoides from UDMA in Iran formed at Late Oligocene - Early Miocene. • Granitoides and enclaves show similair Sr-Nd-Pb isotopic compositions. • They present dominant lithospheric mantle source mixing with lower crustal melts. • They were produced in an extensional regime during slab rollback. [ABSTRACT FROM AUTHOR]

[Display omitted] • Early Carboniferous high-Mg andesitic tuff and diorite were discovered in the Aqishan-Yamansu belt. • The high-Mg rocks were formed by interaction of sediment-derived melts and the depleted mantle wedge. • The Aqishan-Yamansu belt was a continental arc-related basin in the Carboniferous. • The sharp changes of geochemical features in the Aqishan-Yamansu belt indicate an important tectonic transition. The Aqishan-Yamansu belt, Eastern Tianshan is characterized by voluminous Late Paleozoic intermediate–felsic igneous rocks and magmatic–hydrothermal Fe (–Cu) deposits. This study presents zircon U–Pb ages and whole-rock geochemistry of newly identified high-Mg andesitic and dioritic rocks (HMAs and HMDs) within the Hongshanliang copper district in the Aqishan-Yamansu belt, Eastern Tianshan to investigate their petrogenesis and constrain the Carboniferous tectonic setting of the Eastern Tianshan. Zircon U–Pb dating of the HMAs and HMDs yielded ages between 336.9 ± 1.9 Ma and 329.0 ± 4.2 Ma. The HMAs and HMDs show calc-alkaline affinities, and exhibit weak Rb, Ba, U, and Pb enrichment and Nb and Ta depletion, with minor negative Eu anomalies. Moreover, the positive ε Nd (t) values (+6.4 to +6.6), low Th and (La/Sm) N contents/ratios, as well as relatively low and variable ε Hf (t) values (−3.71 to +1.55) indicate that they were probably sourced from a depleted mantle wedge with negligible to minor crustal contamination. They have low Ba/Th ratios (10.8–93.3), minor negative Eu anomalies, high and variable (La/Sm) N and Th/Yb ratios, which are comparable to the well-known sanukites of the Setouchi volcanic belt, suggesting involvement of sediment-derived magmas during their formation. Integrating published regional mafic–intermediate rocks from the Aqishan-Yamansu belt and this study, we propose that the Hongshanliang high-Mg rocks formed in a continental arc-related setting in the Carboniferous and the belt underwent a sharp tectonic transition event (ca. 330–322 Ma) from the Kangguer oceanic slab steepening to breakoff, corresponding to the Late Carboniferous basin inversion. [ABSTRACT FROM AUTHOR]

Distinct types of mafic rocks, including gabbro-norite, gabbro-diorite, and monzogabbro-diorite, are exposed in the southern Chinese Altai. Zircon U-Pb dating of these intrusions reveals that they were emplaced at ca. 283–275 Ma. Geochemical data show that these intrusions are characterized by low Ce/Pb (3.1–10.3), low Nb/U (5.5–38.9), and high Th/Yb (0.4–2.4) ratios. They are slightly LREE enriched, with selective enrichments of LILE and LREE over HFSE and significant Nb-Ta and Zr-Hf depletions. These rocks have depleted Nd isotopic compositions (εNd(t) = 1.8–5.0). In addition, the monzogabbro-diorite samples contain abundant primary amphibole and biotite and show high Rb/Y ratios. The above geochemical characteristics and mineral associations indicate that their parental magmas were hydrous and likely resulted from partial melting of subduction-metasomatized sub-continental lithospheric mantle (SCLM). In contrast, the orthopyroxene-bearing gabbro-norite and gabbro-diorite intrusions show anhydrous and high-T mineral assemblages, implying that the hot asthenosphere must have been also involved in their magma genesis. Given the absence of oceanic island basalt (OIB)-like signals in our samples, the contribution of the coeval Tarim mantle plume can be precluded. A slab break-off scenario is proposed for the Chinese Altai after its collision with the East Junggar in Permian, with products of mafic magmas generated by the interaction between partial melts of SCLM and upwelling depleted asthenospheric mantle. Apart from the Altai Range, the coeval mafic-ultramafic magmatism in the Beishan and East Tianshan orogens share comparable petrogenesis, indicating a general tectonic regime of the western CAOB during this transitional period. • Permian mafic intrusions in the Chinese Altai were formed in an extensional setting. • Partial melting of the SCLM and asthenosphere gave rise to the mafic magmatism. • Upwelling of the asthenosphere was triggered by slab break-off. • A post-collisional tectonic regime prevailed in the western CAOB during the Permian. [ABSTRACT FROM AUTHOR]

[Display omitted] • Newly ca. 880 Ma gabbro-diorite and gabbro are identified in the Bikou Terrane. • Both the gabbro-diorite and gabbro were formed in a subduction-related tectonic setting. • The Bikou Terrane was a part of the subduction-related system during the early Neoproterozoic. The Neoproterozoic mafic intrusions in the Bikou Terrane along the northwestern margin of the Yangtze Block record crucial information on evaluating the tectonic evolution of the Yangtze Block, South China. However, their petrogenesis and tectonic significance are still poorly constrained. In this paper, we present the results of a comprehensive study of zircon U–Pb geochronology and whole-rock geochemistry from the gabbro-diorites and gabbros of the Bikou Terrane. Zircon U–Pb dating results indicate that these gabbro-diorite and gabbro samples were formed coevally at ca. 880 Ma. The gabbro-diorite samples are calc-alkaline in composition and have intermediate contents of SiO 2 , Mg#, Ni, and Cr. They are enriched in LREEs, and depleted in HFSEs (i.e., Nb, Ta, Zr, and Hf). They have relatively high ratios of Th/Yb, and low ratios of Nb/Yb, Nb/La, Th/Nd, Th/Zr, and U/Th, indicating that they were derived from partial melting of a mantle wedge source metasomatized by slab-derived melts. The gabbro samples are commonly classified as sub-alkaline tholeiitic rocks, and have constantly low to medium values of MgO, Mg#, Cr, and Ni, with distinct spikes at Th, U, Nb and Ta concentrations. They show an E-MORB-like enriched LREEs, low ratios of Nb/La, Ta/Yb, Th/La, and Nb/Zr, and medium ratios of Nb/Yb and Th/Yb, implying that they were most probably originated from the interaction between the upwelling enriched asthenospheric mantle and the mantle wedge peridotite. This mechanism may be triggered by the slab rollback process in a subduction-related environment. Our new investigations, along with available observations from other scholars, support the persistent subduction-related system along the northwestern margin of the Yangtze Block during the early Neoproterozoic. [ABSTRACT FROM AUTHOR]

• New geochronological and geochemical data for Devonian lamprophyres and diorites. • The lithosphere mantle of Longshoushan area was metasomatism by the fluids released from the subducting slab of North Qilian. • The 403–374 Ma magmatism reflect the unrooting and collapse of the North Qilian orogen under the effects of convective erosion. The North Qilian orogenic belt (NQOB) has been defined as a subduction-collision zone between the Alxa Block and the Qilian Block during the Early Paleozoic. To constrain the post-collisional tectonic evolution of the NQOB, analyses of zircon U-Pb-Hf isotopes, whole-rock major, trace element and Sr-Nd-Pb isotope compositions of the newly discovered Early Devonian lamprophyres and diorites dikes from the Longshoushan area in southwestern margin of the Alxa Block were conducted. Zircon U-Pb dating yields emplacement ages of 400 ± 4 Ma and 403 ± 6 Ma for two lamprophyre dikes and 391 ± 3 Ma for two diorite dikes. The lamprophyres dikes are shoshonitic-high-K (calc-alkaline) in nature, and are characterized by SiO 2 contents of 53.6–56.3 wt %, (87Sr/86Sr) i ratios of 0.7064 to 0.7072, εNd(t) values of 0.1–1.0, and zircon εHf(t) values of −8.0 to −2.9. The diorite dikes are high-K (calc-alkaline), and are characterized by MgO contents of 6.32–6.98 wt %, (87Sr/86Sr) i ratios of 0.7089–0.7137, εNd(t) values of −3.8 to −3.5, and zircon εHf(t) values of −9.9–0.4. Both the lamprophyre and diorite dikes show parallel enrichments in LREEs and LILEs and depletions in HREEs and HFSEs and have similar ratios of (206Pb/204Pb) i (17.587–18.133), (207Pb/204Pb) i (15.518–15.584) and (208Pb/204Pb) i (37.676–38.058). Geochemical and isotopic data suggest that the lamprophyre and diorite dikes were derived from low-degrees melts of amphibole- and phlogopite-bearing lherzolite and phlogopite-bearing lherzolite, respectively, in the spinel-garnet transition facies. Their parental magmas both experienced extensive fractional crystallization in a deep magma chamber and negligible crustal contamination during their ascent. Regarding the Palaeozoic tectonic development of the North Qilian orogenic belt, we propose that the Early Devonian lamprophyres and diorites possibly are related to North Qilian orogen unrooting and collapse and marking the end of the North Qilian orogenic events. [ABSTRACT FROM AUTHOR]

• Contrasting Neoproterozoic magmatism between the northern and southern South Qinling Belt. • Ca. 850–780 Ma magmatic rocks correspond to syn- and post-collisional magmatism. • Mid-Neoproterozoic tectonic transition from subduction to post-collision. The South Qinling Belt was located in the northernmost domain of the Yangtze Block during Neoproterozoic, and witnessed extensive magmatism in its southern part (<800 Ma) and northern part (>800 Ma). The mechanism and implications of the contrasting magmatism on the southern and northern sectors of this major orogenic belt remain unclear. Here we investigate a suite of magmatic intrusions along the Ningshan-Xianghe Fault that separates these two domains to gain insights into the Mid-Neoproterozoic tectonic processes in the northern segment of the Yangtze Block. LA-ICP-MS zircon U-Pb dating yields ages of ca. 851–783 Ma for the Precambrian stocks along the Ningshan-Xianghe Fault. Our result suggests that the ca. 851 ± 5 Ma Xiaolingguan diorite has an adakitic affinity, and was derived from the partial melting of thickened basaltic lower crust. The ca. 834 ± 4 Ma Yaolinghe diorite was formed through the recycling of Paleoproterozoic crustal materials in a syn-collisional setting. The ca. 783 ± 5 Ma Liangjiawan granite is inferred to have formed by partial melting of crustal high-K metabasaltic rocks in a post-collisional setting. This event may be attributed to a Mid-Neoproterozoic tectonic transition from subduction to collision and post-collision, which gave rise to syn- and post-collisional magmatism in the northern margin of the Yangtze Block. [ABSTRACT FROM AUTHOR]

Two Early-Middle Triassic magmatic arc belts occur in the Indochina Block within Thailand, namely the Lampang Volcanic Belt and the Loei-Phetchabun Volcanic Belt, which are about 150 km apart and run parallel to each other. The Lampang Volcanic Belt has been extensively studied and suggested to be induced by eastward Paleotethyan subduction, whereas the Loei-Phetchabun Volcanic Belt has not been well constrained due to the scarcity of geochronological and geochemical data. Here we report a detailed study on zircon U–Pb dating, elemental geochemistry and Sr–Nd isotopes for the Phu Rai diorites recently identified in Loei Province, NE Thailand. The Phu Rai diorites yield Middle Triassic (ca. 239 Ma) emplacement ages. They are calc-alkaline rocks characterized by arc-like trace element patterns and depleted Sr–Nd isotopic compositions ((87Sr/86Sr) i = 0.70371–0.70392; ε Nd (t) = +1.65 to +2.54). These geochemical and isotopic signatures reveal that the Phu Rai diorites were most likely derived from a depleted mantle wedge metasomatized by subducted sediment-derived melts and slab-derived fluids, and modified by limited degree of fractional crystallization involving clinopyroxene, amphibole and Fe–Ti oxides combined with weak plagioclase accumulation. Based on our results and others from the literature, we suggest the existence of an Early-Middle Triassic (ca. 250–239 Ma) magmatic arc belt in NE Thailand, which is not directly linked to eastward Paleotethyan subduction, but is possibly associated with eastward subduction of the Nan back-arc basin. Specifically, the ca. 239 Ma Phu Rai diorites and ca. 245–241 Ma adakites nearby form a rock association in response to slab break-off at that time, immediately after the initial stage of the Sukhothai-Indochina collision. The occurrence of this rock association could mark not only the cessation of eastward subduction of the Nan back-arc basin but also the initiation of the Sukhothai-Indochina collision. • Middle Triassic (~239 Ma) diorites in NE Thailand. • They exhibit arc-like trace element pattern and depleted Sr–Nd isotopes. • They originated from a metasomatized lithospheric mantle source. • Slab break-off follows the Sukhothai-Indochina initial collision. [ABSTRACT FROM AUTHOR]

• Three episodes of Precambrian mafic magmatism occur in the Chinese Central Tianshan. • The magmatic rocks were derived from partial melting of a fertilized SCLM at different times. • Microcontinents in the western CAOB and the Tarim Craton may share a common geodynamic evolution. Precambrian microcontinents are an essential component in the tectonic evolution and architecture of the Central Asian Orogenic Belt (CAOB). However, the early crustal evolution and origin of Precambrian microcontinents remain poorly constrained due to the scarcity of early Precambrian rocks. The Chinese Central Tianshan Block (CTB) constitutes a microcontinent in the western CAOB with Precambrian basement rocks along its southern margin. The basement rocks, comprising amphibolite-facies supracrustal assemblages of possible volcano-sedimentary origin, are exposed in the Wuwamen Complex, which occurs as tectonic slivers in the late Paleozoic Wuwamen ophiolitic mélange. Here we present in situ zircon U–Pb and Lu–Hf isotopic data and the whole-rock geochemistry of three suites of (meta-)mafic rocks from the Wuwamen Complex and an associated Neoproterozoic gabbro body. The zircon dating revealed that the Wuwamen Complex contains two suites of meta -mafic rocks with protolith formation at ca. 2.55 Ga and 2.21 Ga followed by an amphibolite-facies metamorphic overprint at ca. 1.83 Ga. In addition, an individual gabbro body adjacent to the Wuwamen Complex yielded an emplacement age of ca. 0.69 Ga, reflecting a mid-Neoproterozoic mafic magmatic event in the CTB. Furthermore, zircon U–Pb dating of a crosscutting diorite dyke and a gneissic diorite sourced from a composite batholith in the CTB yielded weighted mean intrusive ages of ca. 320 Ma and 454 Ma, respectively. In conjunction with the field observation, the emplacement ages suggest that the Wuwamen Complex represents a part of the continental arc basement of the CTB. The three suites of (meta-)mafic rocks show geochemical characteristics similar to typical arc-related basalts. Along with the evolved zircon Hf isotopic compositions, it is suggested that these rocks originated from partial melting of a metasomatized sub-continental lithospheric mantle during different events. In conjunction with previous studies, the here presented new data further suggest that the CTB and other microcontinents in the western CAOB record similar Precambrian magmatic and metamorphic episodes, which are comparable to those of the northern Tarim during Proterozoic times. The here outlined new model indicates that the microcontinents of the western CAOB and the Tarim Craton may have shared a common geodynamic evolution. [ABSTRACT FROM AUTHOR]

The granodiorites, monzogranites and diorites are widely developed in the Balikun area of Eastern Tianshan Orogen. Of which, LA–ICP–MS zircon U‐Pb isotopic dating from the diorites revealed that they were emplaced at 327∼333 Ma, representing an important period of magmatism in the Early Carboniferous. Geochemically, they are characterized by moderate SiO2 (51.33–62.48 wt%), high but variable MgO (2.04–11.16 wt%, average 5.35), higher Mg# (40–73) and TiO2 (0.67–1.29 wt%), Na2O/K2O (1.39–2.95) as well as variable Cr (2.49–675 ppm) and Ni (1.31–174 ppm), showing a geochemistry similar to those of high‐Mg diorites or sanukitoids. In addition, they are enriched in the LILE, poor HFSE with an evident negative Nb anomalies and a REE pattern of moderate fractionator between LREE and HREE without or weak negative Eu anomalies. Their ∊Hf(t) are positive (+3.63–+15.65), suggesting a source from the depleted mantle. In addition, they have high TiO2 and Pb, and large quantity of amphibolite and biotite, indicating that they were most likely derived from the partial melting of depleted mantle metasomatized by the slab‐derived melt under a hydrous condition. Consequently, combined with the contemporary volcanics and granitoids formed in the island arc settings, we proposed that the subduction was continued till Early Carboniferous in the Bogda‐Harlik tectonic belt. After that, wide occurrence of the post‐collisional A‐type granites and mafic‐ultramafic intrusions indicate this tectonic belt entered the post‐collisional environment from Late Carboniferous to Permian. [ABSTRACT FROM AUTHOR]