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The Tudigou porphyry Cu deposit is located in the central part of the southern Qinling belt. Copper mineralization is closely associated with monzogranite porphyry. Zircon LA–ICP–MS U–Pb dating of monzogranite porphyry suggests that the ages of magmatism at Tudigou vary between 150 ± 1 and 148 ± 1 Ma and overlap with the molybdenite Re–Os age of 150–148 Ma, indicating that the Tudigou intrusion and associated mineralization formed during the Late Jurassic. The enrichment in large‐ion lithophile elements, depletion in high‐field‐strength elements, high Ba/Th and La/Yb ratios, and negative correlation between Dy/Yb and La/Sm ratios, together with narrow ranges of εHf(t) values (εHf(t) = −4.0 to +1.4) suggest monzogranite porphyry was derived from a metasomatized lithospheric mantle with minor crustal components contribution, which is also evidenced by the lead isotopic result. The La/Yb ratios of 30 Mesozoic plutons in the southern Qinling belt were used to calculate the Moho depth, which suggests that the magmatism and mineralization in the region occurred during lithosphere thinning in response to the tectonic transition from compression to extension transitional regime. The calculated oxygen fugacity of the Late Mesozoic porphyry deposits in the Qinling–Dabie orogen have identical ΔFMQ values (averaging +1.4 to +2.4). However, the V/Sc ratios (the proxy for water content) are distinct among different deposit sizes, indicating that the dissolved water in the magma plays a critical role in porphyry‐type mineralization. [ABSTRACT FROM AUTHOR]

The Inner Mongolia Plateau is located in the north of the Late Palaeozoic Hegenshan ophiolitic mélange belt, and its Mesozoic magmatism impacts our understanding of the tectonic evolution affected by the closing of the Mongol‐Okhotsk Ocean and Palaeo‐Pacific Ocean. Here, we present new U–Pb ages, whole‐rock geochemistry and Hf isotopes from the Late Mesozoic magmatic rocks in the Dalai area along the northeastern margin of the Inner Mongolia Plateau. The Late Jurassic rock types include medium‐fine‐grained phenocryst‐bearing and porphyritic monzogranites as well as medium‐fine‐grained monzogranites with the precise age range of 167.7–159.8 Ma. The Early Cretaceous rock types consist of fine‐grained biotite monzogranite and medium‐fine‐grained biotite monzogranite with the precise age range of 140.9–130.7 Ma. The geochemistry data show that the Late Jurassic and Early Cretaceous rocks are peraluminous granites and high‐K calc‐alkaline series and can be classified as A‐type granite. These granites are enriched in large‐ionlithophile elements such as Rb, Th and U, depleted in the high‐field‐strength elements such as Nb, Sr, P, and Ti. Rare earth elements have high total concentrations and present the light rare earth elements enriched with the heavy rare earth elements depleted. Zircon Hf isotopes show that εHf(t) ranges from +8.0 to +15.9 from the Late Jurassic rocks and +6.9 to +13.5 from the Early Cretaceous rocks. Our new results reveal that the Late Jurassic and the Early Cretaceous magmas were derived from partial melting of the younger lower crust, and the Early Cretaceous rocks are more strongly contaminated than the Jurassic intrusions. The Late Jurassic rocks in the Dalai area were formed from a post‐collisional setting related to the closure of the Mongol‐Okhotsk Ocean in the Early‐Middle Jurassic. The Early Cretaceous intrusions were formed from a transition setting from post‐collision to syn‐collision associated with the superposition of the Mongol‐Okhotsk Ocean and the Palaeo‐Pacific Ocean tectonic domain. [ABSTRACT FROM AUTHOR]

Igneous epidote occurring in tonalite–trondhjemite–granodiorite (TTG) rocks provides valuable insight into the physiochemical parameters of their magmatic system. Epidote has been identified within a newly discovered, rare, Ediacaran, high‐Al TTG‐suite at the Fannani Igneous Complex (FIC), Nubian Shield. The objective is to assess P–T conditions of magma emplacement using petrographic‐, mineral chemical data, and thermobarometry methods. The TTG‐suite is made up of ubiquitous oligoclase, variable contents of quartz, K‐feldspar, amphibole, biotite, epidote, accessory titanite, zircon, apatite and magnetite. Feldspars vary from An14 to An26 in plagioclase, with K‐feldspar having near‐end‐member compositions (Or91–Or95). Amphiboles are Al‐rich (AlT = 1.65–2.04 atoms per formula unit [apfu]), calcic (Ca = 1.83–1.93, apfu), with average Mg/(Fe + Mg) of 0.44, and are ferroedenite–edenite–ferropargasite. Biotites are moderately Fe‐rich (Fe/(Fe + Mg) = 0.50–0.58) characteristic of type 'C'–biotite of calc–alkaline orogenic rocks. Epidote exhibits pistacite components [Ps = Fe3+/(Fe3++Al)] of Ps24–Ps33, typical of magmatic epidote. The average crystallization pressure of 5.41 kbar (calculated using the Al‐in‐Hb barometer) is consistent with the presence of magmatic epidote and reflects the mesozonal crustal levels of emplacement. The Hb–Plag–geothermometer produced an average crystallization temperature of 721°C. These values fall within experimentally‐determined P–T ranges of stability of magmatic epidote with fO2 buffered from nickel‐nickel‐oxide (NNO) to hematite (HM). The FIC rocks were developed from a wet, subsolvus, orogenic, Al‐rich magmatic system. Findings reported here could have implications for conditions of magma emplacement and mineralogical characterization of TTGs occurring within various continental masses. [ABSTRACT FROM AUTHOR]

The Kelameili Ocean was one branch of the Palaeo‐Asian Ocean, the initiation and closure history of which remains elusive. Consequently, they hamper our understanding of the accretionary evolution of the southern Altaids. In this paper, we carried out field mapping and also geochronological and geochemical analyses on the Huangcaopo Group in the northern Harlik Mountains, NW China. Field investigation revealed that "block‐in‐matrix" structure develops with blocks of andesite, limestone, sandstone, and gabbro in matrices of turbidites. Combined with our recent work, our field investigation indicates that the Huangcaopo Group is the southern extension of the Kelameili accretionary complex. A gabbro block (19HAM057) was dated at 500 ± 4 Ma, its geochemical affinity was defined to be similar to arc magmatic rocks. Magmatisms represented by two gabbroic intrusions (19HAM057‐2 and 19HAM048) were dated at the latest Devonian (360 ± 5 Ma) and the latest Carboniferous (299 ± 4 Ma), respectively. Their geochemistry displays enrichments in light rare earth elements (LREE) and large ion lithophile elements (LILE), but depletions in high field strength elements (HFSE, especially Nb and Ta). And a younger gabbroic intrusion (19HAM052) yielded crystallization age of the latest Permian (254 ± 3 Ma), and its geochemistry also shows affinity to arc magmatism. The magmatism represented by the gabbro block (19HAM057) was coeval with the Zhaheba‐Aermantai ophiolite, indicating that it was the product of incipient arc magmatism following subduction initiation in the Kelameili branch of the Palaeo‐Asian Ocean. However, two episodes of gabbroic magmas (19HAM057‐2 and 19HAM048) that intruded the Kelameili accretionary complex from the latest Devonian to latest Carboniferous indicate southward rollback of the subducting Kelameili oceanic lithosphere and resulted in the development of a growing arc. Meanwhile, the youngest gabbroic intrusion (19HAM052) suggests that northward subduction of the Kelameili oceanic lithosphere may have at least lasted to the latest Permian, indicating that the closure of the Kelameili Ocean might have been later than the latest Permian, most likely in the early Triassic. Our new data provide further constraints on the initiation and closure history of the Kelameili Ocean, which shed light on the accretionary evolution of the Altaids. [ABSTRACT FROM AUTHOR]

Granitoids and their mafic microgranular enclaves (MMEs) provide important insights into magmatic activity and tectonic evolution associated with accretionary orogens. Here we investigate the origin of Middle Triassic granodiorites and MMEs in the central segment of the eastern Kunlun Orogen (EKLO) in NW China, which is an important region to evaluate the history of closure of the Paleo–Tethys, through zircon U–Pb geochronology, major and trace element geochemistry, and Sr–Nd–Hf isotopes. Zircon U–Pb ages indicate the coeval formation of granodiorites and their MMEs during the Anisian (ca. 245 Ma). The granodiorites are calc‐alkaline and metaluminous with high SiO2 contents and Mg# values. They are characterized by enrichment of LREEs and LILEs, and depletion of Nb, Ta, and Ti. Their Sr–Nd –Hf isotopic compositions indicate that the magmas were derived from enriched mantle and Paleoproterozoic basement. The monzodioritic‐dioritic MMEs exhibit low SiO2 contents and high Al2O3 and MgO with high Mg# values, enrichment in LREEs and LILEs, and depletion in HFSEs with negative Nb, Ta, Ti, and P. In contrast, the gabbroic MMEs show higher Mg# values and Cr contents. Both types of MMEs have Sr–Nd–Hf isotopic compositions similar to the host granodiorites, and originated from mixing of lower crust‐ and enriched mantle‐derived magmas. The mantle‐derived sources were metasomatized by slab‐derived melts. The Middle Permian to Middle Triassic magmatism, metamorphism, sedimentation, and tectonics in the EKLO suggest northward subduction of the Paleo–Tethys Ocean as represented by the A'nyemaqen Ocean. The magma mixing that generated the Anisian granodiorites and MMEs was likely associated with slab break‐off of the Paleo–Tethys Ocean. The formation of the Anisian magmatic rocks in the EKLO suggest that the cessation of subduction of the Paleo–Tethys Ocean and onset of collision took place during the late stage of Middle Triassic. [ABSTRACT FROM AUTHOR]

The origin of high Ba‐Sr magmatic suites with adakitic features has remained controversial, although they provide important clues on the evolution of continental lithosphere. Here, we present petrological, geochemical, zircon U–Pb and Lu‐Hf data from an Early Cretaceous volcanic suite of andesitic‐dacitic composition in the Laiyuan complex of the central North China Craton, with a view to gain insights on the magma source, petrogenesis, and tectonic implications. The volcanic suite represented by rocks of andesitic‐dacitic composition shows enrichment in light rare earth elements (LREE) and large‐ion lithophile elements (LILE), and depletion in high‐field‐strength elements (HFSE) with no obvious Eu anomalies. They also show typical adakitic features such as high Sr/Y and La/Yb ratios, as well as high Ba‐Sr concentrations. Zircon U–Pb geochronology indicates that these rocks were formed in Early Cretaceous during 131 to 127 Ma, with εHf(t) values ranging from −23.5 to −19.4, suggesting enriched lithospheric mantle source. The geochemical and isotopic data show that the enriched lithospheric mantle source experienced fluid‐related subduction metasomatism. The distinct geochemical features of these identified in our study including high Ba‐Sr concentrations and adakitic affinities were not only inherited from their magma source, but are also a result of fractional crystallization during magma evolution including amphibole‐dominated fractional crystallization at depth and limited plagioclase removal. The volcanism in the Taihang Mountains occurred under extensional regime triggered by the subduction and rollback of the Paleo‐Pacific slab during Late Jurassic to Early Cretaceous and consequent thermal‐mechanical erosion of the lithospheric mantle. [ABSTRACT FROM AUTHOR]

Comprehensive petrological, zircon U–Pb dating, whole‐rock geochemical, and Sr–Nd isotopic data are reported for the Duobagou volcanic rocks, intercalated with terrigenous clastic sequence, composing former Jurassic strata located at southeastern Dunhuang region, NW China. Duobagou volcanic interlayer is mainly composed of trachyandesite. LA–ICP–MS zircon dating yields a weighted mean 206Pb/238U age of 201.4 ± 3.4 Ma, affirming the formation of Late Triassic. The trachyandesites are characterized by enrichment of LREE relative to HREE with negative Eu, Sr, and Ti anomalies. The εNd(t) values (−0.24–1.91) and (87Sr/86Sr)i (0.7037–0.7049) shows an affinity of OIB. The Duobagou trachyandesite and Lucaogou basalt were proposed to be produced via 1–5% and 10–20% partial melting of the spinel–garnet‐bearing metasomatic enriched mantle and crystal fractionation coupled with slight extents of crustal contamination. Due to the delamination of thickened continental crust and asthenosphere upwelling, lower crustal material metasomatized and enriched the mantle source, leading to the eruption of trachyandesite. The Duobagou trachyandesite, Lucaogou sub‐alkaline basalt and thick sedimentary strata revealed that the Dunhuang region remained in an extension setting accompanied by rifting from Late Triassic to Middle Jurassic. [ABSTRACT FROM AUTHOR]

Potassic magmatic rocks provide significant insights in understanding of mantle composition, evolution, and interaction with crust. Potassic magmatism along the Jinshajiang–Ailaoshan Paleo‐Tethyan suture has drawn much attention. Whereas igneous intrusion in the Simao terrane, west to Jinshajiang–Ailaoshan potassic magmatic belt has rarely been investigated. Hence, we present zircon U–Pb ages and Lu–Hf isotope and whole‐rock geochemistry for the Lianhuashan pluton. Zircon U–Pb dating from monzonite and quartz monzonite porphyry yield ages of 33.6 ± 0.2 and 33.5 ± 0.3 Ma, respectively. Monzonites are characterized by high K2O (4.93–5.16%) and K2O/Na2O (1.46–1.71), high Y (22.90–23.80 ppm), and Yb (1.87–2.21 ppm), relatively enrichment of light rare earth element (LREE). Zircons from monzonites show εHf(t) values ranging from −1.1 to +0.6 and crustal model ages (TDMC) between 1.04 and 1.15 Ga. These geochemical features suggest that parent magmas of the rocks originated from a metasomatized lithospheric mantle. Quartz monzonite porphyries are characterized by high Sr (836.00–1,529.00 ppm), Sr/Y (70.85–99.93) and La/Yb (32.31–49.83), low Y (11.80–15.60 ppm), and Yb (0.95–1.30 ppm), enrichment in LREE and depletion in heavy rare earth elements (HREE). Quartz monzonite porphyries have higher Mg#, MgO, Ni, and Cr contents than the lower crust‐derived adakite‐like rocks. It is suggested that they were derived by variable degree of mixing between lower‐crustal melts and mafic magmas. Based on petrology and geochemistry features, the following evolution process are concluded. During the Neoproterozoic, metasomatic‐enriched mantle magma resulted from the bisubduction of oceanic plate; meanwhile, the crust thickened, and juvenile lower crust formed. During late Eocene, hot asthenosphere upwelled and K‐rich mafic magmas resulted from the decompression of delamination, followed by magmatism emplacing, crystallizing, and the forming of the Lianhuashan pluton. [ABSTRACT FROM AUTHOR]

This study presents new zircon U–Pb ages, Sr–Nd–Hf isotopic data, and whole‐rock geochemical data obtained from the Early Cretaceous volcanic rocks from the north‐western Great Xing'an Range, Northeast China, to constrain the late Mesozoic magmatism and geodynamic setting of this region, which is located in the eastern segment of the Central Asian Orogenic Belt (CAOB). Zircon U–Pb age determinations show that the studied samples formed at 124–114 Ma with an Early Cretaceous magmatic event produced voluminous felsic and minor mafic volcanic rocks. The mafic rocks are dominantly basalt and basaltic andesite, with relatively low SiO2 contents (49.88–56.64 wt.%). These rocks are enriched in Th, U, large‐ion lithophile elements (LILE; e.g., Rb, Ba, and K) and light rare‐earth elements (REEs), and depleted in high‐field‐strength elements (HFSE; e.g., Nb, Ta, and Ti) and heavy REEs (Yb and Lu). The rocks have εNd(t) values of 0.44–0.75 and initial 87Sr/86Sr ratio of 0.70499–0.70548. These results indicate that the mafic rocks were derived from the partial melting of enriched lithospheric mantle that had been previously metasomatized by subduction‐related fluids and experienced variable amounts of fractional crystallization and moderate crustal contamination. In contrast to the mafic rocks, the felsic rocks are dominantly peraluminous trachytes, rhyolites, and dacites with high SiO2 contents and low MgO contents. These felsic rocks display enriched and variable concentrations of LILEs and REEs, show negative Eu anomalies, and have εHf(t) values of +2.6 to +8.3 with TDM2 ages of 1,014–655 Ma, indicating they were derived from partial melting of juvenile crustal materials. These Early Cretaceous igneous rock assemblages record a post‐collisional lithospheric extensional setting resulting from the closure of the Mongol–Okhotsk Ocean, consistent with the results of previous studies on the contemporaneous tectono‐magmatic activities in NE China. [ABSTRACT FROM AUTHOR]

We performed geochronological and geochemical analyses of granitoids in the Langshan Tectonic Belt (LTB), southwest of the Solonker suture zone, for the determination of its age, petrogenesis, and tectonic setting, which are crucial for unravelling the Permian tectonic evolution in the south‐eastern Central Asian Orogenic Belt (CAOB). It is indicated by zircon U–Pb ages together with previous ages that the Permian igneous rocks within the LTB can be grouped into two episodes. The Early‐Middle Permian (~281–268 Ma) granitic intrusive rocks are mainly I‐type granitoids characterized by lithophile element enrichments, high‐field‐strength element depletions, and obvious negative Nb‐Ta‐Ti anomalies. These granitic intrusive rocks are further high‐K calc‐alkaline, arc‐related granitoids. In contrast, the Late Permian‐Middle Triassic (~260–241 Ma) granitoids contain relatively high SiO2, Al2O3, and Sr contents, but relatively low Y (Yb) contents and Mg# values, resembling the post‐collisional granitoids. Hf isotopic compositions of the two‐stage granitoids show similar features with both positive and negative values. The εHf(t) values of the four samples from −2.6 to +4.8 record predominantly Meso–Neoproterozoic crust components. According to the regional geological investigations and geochemical data, we suggest that the Early‐Middle Permian arc‐like granitoids formed in continental arc setting, which represents the final stage of Paleo‐Asian Oceanic subduction, and then the Late Permian‐Middle Triassic adakitic granitoids were probably formed in a post‐collisional setting due to the final closure of the Paleo‐Asian Ocean. [ABSTRACT FROM AUTHOR]

The Central Tianshan microcontinent (CTM) in the southern Central Asian Orogenic Belt is characterized by Precambrian crustal basements and widespread Palaeozoic granitic rocks. However, the Palaeozoic tectonic process and associated crustal evolution of the CTM have not been well constrained. In this paper, we report whole‐rock geochemistry, zircon U–Pb ages, Hf isotopes, and trace elements for the Late Carboniferous granodiorite and monzogranite from the Hongliujingbei area of the eastern CTM. These data were further integrated with previously published whole‐rock geochemistry and zircon Hf isotopic data of the intensive Late Carboniferous (327–300 Ma) magmatic rocks in the CTM in order to gain more insights into the crustal and tectonic evolution of the CTM during the Late Carboniferous. LA‐ICP‐MS zircon U–Pb dating results indicate that the granodiorite and monzogranite from the Hongliujingbei area were emplaced at ~320 Ma. Their highly variable zircon εHf(t) values (−0.1 to +12.9) suggest that the magmas of these rocks were formed by the mixing of mantle‐ and crustal‐derived magmas. The Late Carboniferous magmatic rocks from the CTM, as a whole, show a wide range of zircon εHf(t) values (−3.7 to +13.4) and geochemical characteristics typical for magma evolution in an active continental margin setting. Therefore, we suggest that the Late Carboniferous magmatic rocks in the CTM were probably generated in a continental arc formed by the southward subduction of the North Tianshan Ocean Plate beneath the CTM, and their mostly depleted zircon Hf isotopic compositions indicate that juvenile crustal growth was a dominant process in the CTM during the Late Carboniferous. [ABSTRACT FROM AUTHOR]

Constructing the plutonic–volcanic connections in volcanic arc setting is essential for understanding a variety of magmatic processes from continental crust differentiation to formation of magmatic‐hydrothermal ore deposits. Based on the combination of zircon U–Pb geochronology and Hf isotope and whole‐rock geochemistry and Sr‐Nd isotopes, we evaluated the potential connections between volcanic and plutonic rocks from the Tulasu Basin, the largest epithermal gold ore district in the Chinese Western Tianshan. The peak of volcanism coincides well with the major plutonism, representing an important magma event at ~347–367 Ma. These contemporaneous volcanic and plutonic rocks show broadly similar arc‐related geochemical signatures and zircon in‐situ Hf (εHf[t] = −1.0–14.3) and whole‐rock Nd (εNd[t] = −4.2–4.6) isotopic compositions, indicative of formation from parental magmas derived from a common depleted mantle source metasomatized by slab‐derived melts, despite diverse consequent processes (fractional crystallization, crustal contamination, and magma mixing/mingling) during their differentiation in a subduction‐related setting. Volcanic rocks from the Axi caldera in the centre of the Tulasu district are geochemically less evolved than the coeval porphyritic granite, which indicates that the intrusive rocks might originate from residual melts left behind by extraction of erupted magmas. In contrast, the porphyry Cu mineralized Kexiaxi pluton, which occurs in the margin of the Tulasu district, is compositionally indistinguishable from the coeval volcanic suites. This implies that the Kexiaxi pluton represents the intrusive equivalent of a common magma reservoir feeding the volcanic eruptions, and magma fluxes may have controlled their differentiation. We thus suggest that the depleted mantle derived calc‐alkaline magma, modified during slab‐related melt metasomatism, crustal contamination, and magma mixing may have played an important role in copper enrichment at Kexiaxi. Finally, the relatively water‐rich and fertile nature of arc magma of the Tulasu district indicates high exploration potential for significant porphyry Cu‐Au deposits. The existing alteration‐immobile fertility proxy (V/Sc) for intrusive rocks may also be useful to assess the fertility of cogenetic volcanic rocks, in turn with implications for unexposed porphyry Cu deposits at depths. [ABSTRACT FROM AUTHOR]

The Chinese Central Tianshan Arc Terrane (CTA) in the southern Central Asian Orogenic Belt is characterized by voluminous Palaeozoic to Mesozoic (500–240 Ma) granites, with a magmatic "flare‐up" at Early Permian time (ca. 280 Ma). However, the tectonic setting of the Early Permian granites in the CTA is highly debated. In this study, Early Permian (ca. 280 Ma) granitic intrusions, including quartz diorite and dioritic enclave, amphibole granite, biotite granite, dioritic porphyry dyke, and a weakly mylonitic granitic dyke, were revealed from the Xingxingxia area of the CTA by LA‐ICP‐MS zircon UPb dating. These granitic rocks show magnesian and calc‐alkaline affinities and are characterized by Nb, Ta, P, Ti, and MREE depletion [(Dy/Yb)N = 1.02–1.51] with no significant Eu anomalies, suggesting geochemical characteristics of typical active continental margin magmatic rocks. Zircon trace element geochemistry of these Early Permian granitic rocks also indicates a continental arc setting with high U/Yb and Gd/Yb ratios. Among these granitic intrusions, the dioritic porphyry dyke has negative zircon εHf(t) values (−8.0 to −5.7), suggesting that the magma was produced by partial melting of the ancient crustal basements of the CTA. The rest intrusions show positive but largely varied zircon εHf(t) values of +4.1 to +10.9 (5 samples), suggesting that the magmas were probably derived from the mantle wedge with variable contributions from ancient crustal component during the magma evolution. These granitic intrusions were coeval with high‐temperature metamorphic rocks, mafic‐ultramafic rocks, and Cu‐Ni sulphide deposits in the CTA. Therefore, we propose a geodynamic model of oceanic ridge subduction of the South Tianshan Ocean during Early Permian involving upwelling of asthenospheric mantle through slab window and partial melting of the mantle wedge. The multiple‐derived magmas, including those from mantle wedge and/or ancient crustal basement, and their blendings formed the studied Early Permian granitic associations in the CTA. [ABSTRACT FROM AUTHOR]

Silicate melt inclusions (SMIs) in olivine, clinopyroxene, and orthopyroxene in basalt and trachyandesite of the middle Okinawa Trough (MOT) and in basaltic andesites of the southern Okinawa Trough (SOT) were investigated in detail to understand the evolution of magma and geochemical characteristics of the basaltic magma source. Both the SMIs and host bulk rocks are more heavily enriched with Pb and large ion lithophile elements than with high field strength elements and rare earth elements. The major element compositions of SMIs in the MOT trachyandesite show a scattered variation trend of medium‐K to shoshonitic series and suggest that a K‐rich magma source may exist in the Okinawa Trough. Two groups with distinct element distribution patterns observed in SMIs of the MOT trachyandesite may represent magmas with different evolutionary histories. Compared with fractional crystallization and partial melting processes, magma mixing may serve as a reasonable process for the production of trachyandesite in the MOT. Fractional crystallization has played an important role in basaltic magma evolution in the MOT and SOT. Simulations conducted using MELTS show that the fractional crystallization evolution trends observed correspond well to the presence of a magma chamber at 300 MPa with an H2O content level of 0.2 wt% in the MOT and to the presence of a magma chamber at 300 MPa with an H2O content level of 0.4 wt% in the SOT. Ratios of incompatible trace elements (e.g., Th/Ce, Th/Sm, Ba/Th, and Th/Nb); positive Pb anomalies; negative Nb, Ta, and Ti anomalies; and the existence of organic hydrocarbons (CnHm) in the SMIs can be attributed to the involvement of subducted sediment from the subducting slab. Modelling results suggest that more primitive magma represented by SMIs from the MOT has formed through the melting of less than 6% of a metasomatized depleted mantle with contributions of 1.2% sediment melt and 0.8% sediment fluid. In contrast, more primitive magma from the SOT formed through the melting of 4–10% of the depleted mantle with contributions of 3% sediment melt and 1% sediment fluid. The different features of the SMIs together with different tectonic settings of the MOT and SOT have formed in response to the westward subduction of the Philippine Sea Plate. [ABSTRACT FROM AUTHOR]