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A comprehensive whole-rock geochemical and mineral chemistry study was carried out of granites from the Narnaul and surrounding isolated hills of North Delhi Mobile Belt, NW India to constrain their genesis, and tectonic environment. The distinctive features of granites are meta to peraluminous nature and decreasing trend of P2O5 with high SiO2 (>71%) ascribed to its metaigneous origin. In detail the chemical diversity of the studied samples is reflected by their affinity to Calc-alkaline to shoshonite series with high K2O/Na2O (mostly>1), low MgO (< 0.11%) and variation in Mg# (upto 0.5) and maficity with increasing SiO2. The positive Eu anomalies, high LILE, highly enriched LREE (La/Sm = 4.13@#@19.33) pattern and comparatively elevated concentrations of Cs, La, Ta, Dy, Zr, Pb and Yb suggest different episodes of magmatic differentiation. Our data indicate that melting of older subduction-related igneous rocks and the underwent fractional crystallization in hydrous conditions is the possible mechanism for the generation of I-type granites in collisional tectonic setting. [ABSTRACT FROM AUTHOR]

The locality Janoch (ETE-south) situated nearby the Temelín nuclear power plant (Czech Republic, South Bohemian Region) was chosen out of nine possible localities as a suitable deep radioactive waste depository. Based on further geological, geochemical, geophysical and hydrological studies a suitable area for a potential radioactive waste depository was defined. Furthermore, in this area two homogeneous blocks (eastern block and western block) representing the insulation part of the depository were defined. Both homogeneous blocks are located in the Varied unit of the Moldanubian domain composed of metamorphic rocks (up to Precambrian in age) intruded by Variscan igneous rocks. The only inhomogeneity are intercalations of calc-silicates, marbles and quartzites and also some brittle structures related to the presence of the intercalations. New geological and geophysical mapping helped to improve on the existing results and defined dip and dip direction of the intercalations, their thickness and orientation as well as their range in depth. Petrological, geochemical and hydrological research focused at karstification features related to the presence of isolated lenses of marbles and calc-silicates. Marbles are alternating with calc-silicates, but also with non-karst rocks. They vary in colour, grain size and often contain high proportion of insoluble minerals. In the Moldanubian domain, typical surface karst features as sinkholes, surface stream sinking or springs of karst water are rare and the role of mechanical erosion by ground water on cavity formation and growth is very limited. The origin of the karst features here is mostly related to corrosion. Corrosion is either controlled by the rain water or more commonly by chemically aggressive water from the non-karst host rock that accumulates easily in the more permeable marbles. Dissolution occurs mostly near cracks, joints, faults and fault zones. Some cavities can develop along contacts between marbles and non-karst rocks, which are often related to the presence of brittle structures. The back-reaction of calcium carbonate precipitation is not important here and results only in formation of secondary surface features as for example travertine filling of cavities in non-karst rocks. Besides that, on the locality of ETE-south (Janoch), one of the marble intercalations developed a small karst system with several small caves with speleothems, karst spring and calcareous tufa deposit. The largest cave was around 15 m long and was almost completely destroyed by marble mining activities in the early 1950s. [ABSTRACT FROM AUTHOR]

On the basis of the mineralogical-petrographic and geochemical study of igneous rocks of intermediate composition of the Pripyat complex of the Late Devonian Pripyat–Dnieper magmatism area, two subphases of the Pripyat magmatism phase have been distinguished: late Fransian (Chernin or Skolodino–Chernin) with potassium specification and early Famennian (Turov–Drozdov (Yelets)) with potassium-sodium specification. For the first time, the U–Pb age of titanite from trachyandesites of the parametric Pribor borehole was estimated for rocks of Pripyat–Dnieper magmatism area at 364 ± 1 Ma. These data confirm the Famennian age of the Yelets subphase of the Pripyat phase of magmatism and make it possible to estimate the duration of the magmatic activity of this structure at least 14 m.y. taking into account the isotope dating of the earliest phases of magmatism in the Pripyat–Dnieper–Donetsk Paleorift Structure as 388 ± 12, 383.3 ± 3.8, 384.7 ± 3.9, and 383.6 ± 4.4 Ma in the Azov Region and 381 ± 2 Ma in the Pripyat–Dnieper magmatism area. [ABSTRACT FROM AUTHOR]

Abstract—The results of study and comparison of geochemical characteristics of quartzite sandstones of the Upper Riphean Khobeyu and Lower Paleozoic Obeiz formations of the Circumpolar Urals are presented. It has been established that the composition of quartzite sandstone of both formations was formed mainly from recycled material of ancient metaterrigenous rocks, with the participation of destruction products of igneous rocks of felsic (Obeiz Formation) and basic (Khobeyu Formation) composition and weathering crust material. The accumulation of the Lower Paleozoic psammites was accompanied by a gradual change of clastic sources, with increasing contribution of granitoid clastics. [ABSTRACT FROM AUTHOR]

This study focuses on the igneous rocks composing the Odikhincha massif. The massif is typical ring alkaline–ultrabasic massif with carbonatites, second largest in the Maimecha-Kotui province. The Sr-Nd isotopic values of the traps of the Arydzhang Formation and the host dolomites were also determined for comparison. The Rb–Sr isotope system of phlogopite and calcite from the Od-16-19 carbonatite of the Odikhincha massif is disturbed; the obtained age on the mineral isochrone (245 ± 3 Ma) is close to the time of formation of the Siberian traps and rocks of the ultrabasic–alkaline Maimecha-Kotui complex, but the large scatter of analytical points (MSWD = 22) does not allow this date to be considered as reliable. The disturbance of the isotope system is probably related to the fact that the strontium isotope ratio in the fluid was not constant during autometasomatic phlogopitization of carbonatite. The U–Pb isotopic system of titanite and perovskite from the same carbonatite sample Od-16-19 also appeared to be disturbed, since data points formed discordia. The U–Pb age obtained for titanite and perovskite are 244 ± 5 Ma (MSWD = 1.8) and 247 ± 18 Ma (MSWD = 4), respectively. Apparently, the age values provided by the two isotopic systems (245 ± 3 Ma by Rb–Sr and 247 ± 18 and 244 ± 5 Ma by U–Pb) are consistent with each other and reflect the time of metasomatic processes, i.e., phlogopitization and iolitization. Rb–Sr and Sm–Nd isotope data for ultrabasic–alkaline intrusive rocks with carbonatites of the Odikhincha massif and volcanics of the Arydzhang Formation indicate an enriched, relative to the composition of the convecting mantle, isotopically heterogeneous source of their parent melts. This source could be a combination of ultrabasic mantle rocks and rocks of basic composition (basites). The latter played the role of an enriched component. No signs of contamination of the melts with the host sedimentary rocks in situ were found, however, variations of Sr and Nd isotopic ratios in the rocks of the Odikhincha massif may indicate that during the introduction of deep magmas their interaction and substance exchange with the surrounding rocks of the lithosphere continued up to complete solidification of the melts, as indicated by the nature of local isotopic heterogeneity within the Odikhincha intrusion. [ABSTRACT FROM AUTHOR]

To investigate the thermal structure of central Te Riu a Māui/Zealandia continent we estimate the depth to base of magnetic sources (DBMS), using an updated compilation of magnetic data. We calculate thousands of power spectral density estimates and solve an analytic solution for the fractal distribution of magnetization using a Bayesian method constrained by a sediment thickness model. Our DBMS results are broadly similar to a global model yet show complex relationships with independent models of crust and elastic thicknesses, and depth to base of seismicity (D90). Across central Zealandia, DBMS occurs above, coincident with, and below the Moho reflecting that factors additional to temperature influence DBMS. Away from subduction zones crustal thickness likely modulates DBMS while plate margins show varying influence dependent on margin characteristics. In the Taupō Volcanic Zone we interpret DBMS to reflect Curie point temperature at an average depth of 9–11 km. Error analysis shows that the choice of prior influences the posterior standard deviation and can result in counter intuitive error versus DBMS relationships. We use the DBMS as a basal temperature isotherm in heat flow models to compare with heat flow derived from borehole temperature measurements. Using the standard Curie point temperature of 580°C we find that DBMS derived heat flow models over estimate heat flow in areas underlain by plutonic rocks. We propose this reflects a higher titanomagnetite content in these rocks, although detailed studies of the magnetic mineralogy of Zealandia's plutonic rocks are required. Plain Language Summary: Knowledge of the thermal structure of the crust is fundamental for understanding many geologic processes. Here we have analyzed a new compilation of magnetic data over central Zealandia continent, including onland New Zealand, and calculated the depth to base of magnetic sources (DBMS) which often reflects the 580°C isotherm, known as the Curie point temperature. We find complex relationships between DBMS and markers such as the crust and elastic thickness and depth to which earthquakes occur, reflecting a range of processes additional to temperature influence DBMS. We use the depth to base of magnetic sources to generate heat flow models based on the assumption that magnetization in rocks vanishes at the Curie point temperature. In our study we find that this assumption may be incorrect in some regions dominated by plutonic igneous rocks as the derived heat flow is too high compared to heat flow derived from borehole temperature measurements. A Curie temperature of 500°C better fits observed data. One explanation is that magnetite in these rocks has a higher titanium content which acts to lower the Curie point temperature. Key Points: Depth to base of magnetic sources (DBMS) is shallower, coincident with, and in places deeper than Moho across Zealandia while plate margin style has variable impact on DBMSTo match borehole observations DBMS derived heatflow models require transient properties and a spatially variable Curie temperatureChoice of model prior influences error distribution in Bayesian DBMS determinations and can lead to counter intuitive results [ABSTRACT FROM AUTHOR]

The igneous rocks of Cerro Cacheuta are considered a typical expression of the Permian-Triassic magmatism within the Andes Precordillera of Mendoza, Argentina. In particular, the southwestern margin of this hilltop is characterised by intermediate volcanic and felsic intrusives from the Choiyoi Group, one of the most extensive volcano-sedimentary suites of southern South America. The Choiyoi magmatism is widely associated with dramatic tectonic and environmental changes in the Gondwana supercontinent. Therefore, a better characterisation of the igneous facies of Cerro Cacheuta is critical to understand the evolution of Gondwana and recognise the multiple events that occurred towards the end of the Permian. This paper presents new data about the mineralogy, petrography, and geochemistry of the plutonic and volcanic units of Cerro Cacheuta, which enables authors to draw additional conclusions about the genesis and evolution of the magmatism in the region. Microscope observations indicate that the volcanic rocks are largely consistent with intermediate facies dominated by a porphyry texture with plagioclase and sanidine phenocrystals within a trachytic groundmass. Coetaneous breccias of possible hydrothermal origin and geodes with cryptocrystalline silica, limonite, and quartz are also recognised in outcrops. Geochemical analysis suggests that the lavas would likely correspond to andesites from a calc-alkaline magmatic arc. Furthermore, trace elements show enrichment in LREE/HREE, a slight negative anomaly in Eu, and concentration ratios compatible with crustal extension during the initial stages of the Choiyoi Group. Based on their chemical similarities, the monzonites of the Boca del Río Pluton would correlate with the lower section of the Choiyoi Group, of Permian age. In contrast, granites of the Cacheuta Pluton show a signature typically recognised in units from the Triassic and, therefore, would be comparable to the upper member of the Choiyoi Group. [ABSTRACT FROM AUTHOR]

The southern Great Xing'an Range is located in the eastern Central Asian Orogenic Belt, where voluminous igneous rocks developed during the Late Mesozoic period. The east slope of the southern Great Xing'an Range has been the topic of numerous debates on the level of influence of the Mongol-Okhotsk and the Paleo-Pacific regimes in the Late Mesozoic period. Therefore, this area is a suitable region in which to study the temporal changes in magma sources and tectono-magmatic evolution. In this paper, whole-rock geochemical data, zircon U-Pb geochronology, and zircon Hf isotope studies were carried out on the granitoids in the east slope area of the southern Great Xing'an Range. LA-ICP-MS zircon U-Pb dating revealed the ages of four granitoid samples: 135.0 ± 0.6 Ma, 130.7 ± 1.4 Ma, 130.4 ± 1.0 Ma, and 127.6 ± 0.8 Ma, respectively. The Hf isotope values 176Hf/177Hf = 0.282751–0.283015, εHf (t) = +2.0~+11.5, and T2DM = 583~1442 Ma suggest that the magma was generated by partial melting of Meso- and Neoproterozoic accreted and thickened low crust. The whole-rock geochemical data implied that these granitoids are A-type granite and their formation is closely linked to the subduction of the Paleo-Pacific Ocean plate. These geochemical, isotopic, and geochronological data suggest that the Early Cretaceous magmatism in the east slope area of the southern Great Xing'an Range formed in an extensional back-arc tectonic setting associated with the slab roll-back of the Paleo-Pacific plate subduction. [ABSTRACT FROM AUTHOR]

The evolution and final closure of the Neo-Tethys Ocean are one of the most important geological events that have occurred on Earth since the Mesozoic. However, the evolution of the Neo-Tethys is not well constrained, in particular whether its opening occurred in the Permian or the Triassic and whether a plume was involved with its opening or not. In this study, we present geochronological and geochemical data for mafic igneous rocks in mélanges along the Yarlung Zangbo suture zone (YZSZ) in southern Tibet to constrain the timing and mechanism of opening the Neo-Tethys Ocean. Based on field observations, the YZSZ mélanges can be divided into three segments. The western (west of Zhongba) and eastern (Sangsang-Renbu) segments are composed of ocean plate stratigraphy representing accretionary complexes that formed during subduction of Neo-Tethyan oceanic lithosphere beneath the southern margin of the Asian continent. Mélanges in the central segment (Zhongba-eastern Saga) typically have a siliciclastic matrix, and represent Tethyan Himalayan strata that were structurally mixed with the southern margin of the Asian continent. Based on our and previously published geochemical data, the mafic rocks in the YZSZ mélanges are ocean island basalt (OIB)-like, with ages in the Late Permian-Middle Triassic, the Middle-Late Jurassic, and the Early Cretaceous, respectively. An OIB-like block with an age of ca. 253 Ma is identified from the Zhongba mélanges in the western segment, and it is the oldest OIB lithology yet identified in the YZSZ mélanges related to the evolution of the Neo-Tethys Ocean. Geochemical features indicate that this OIB-like block is distinct from typical OIBs and would be formed during continental rifting to incipient seafloor spreading. In the framework of plate divergent-convergent coupling systems and based on literature data for early Middle Triassic seamounts, radiolarian cherts, and normal mid-ocean ridge basalt-like oceanic crust, we conclude that opening of the Yarlung Zangbo Neo-Tethys Ocean would mainly occur at ~250–243 Ma in the Early Triassic, not later than the early phase of Middle Triassic. In addition, a mantle plume was not involved in opening the Yarlung Zangbo Neo-Tethys Ocean. On the other hand, we have also identified a suite of ca. 160 Ma OIB-like basaltic sills from the Bainang mélanges in the eastern segment, which is the same age as the OIB lithologies previously reported in the Zhongba mélanges. Based on the sill-like occurrence and absence of plume-related rock associations in this region, the Bainang OIB-like rocks might result from Middle-Late Jurassic continental rifting in northern Gondwana. Magmatism related to this tectonic event is preserved in both the YZSZ mélanges and Himalayan strata, but its tectonic significance requires further investigation. Based on this study of the YZSZ mélanges and the previous studies of YZSZ ophiolites, Gangdese belt igneous rocks, and sedimentary rocks, we have reconstructed the entire Wilson Cycle of the Yarlung Zangbo Neo-Tethys Ocean, mainly involving continental rifting and ocean opening, subduction initiation, ultraslow-spreading ridge-trench conversion, subduction re-initiation, and oceanic closure and initial India-Asia collision for the tectonic emplacement of ophiolites. These processes were associated not only with magmatic flare-ups and lulls in the Gangdese belt but also with two stages of ophiolite obduction. Our data therefore provide new insights into the evolution of the Yarlung Zangbo Neo-Tethys Ocean and related Tethyan geodynamics. [ABSTRACT FROM AUTHOR]

Late Precambrian–Early Paleozoic igneous rocks constitute volumetrically minor components of the Iranian Plateau but preserve important information about the magmatic and tectonic history of the northern Gondwana margin. The Chadormalu intrusions are part of Central Iran, which includes Late Precambrian–Early Paleozoic continental crust that is now embedded in the Alpine-Himalayan orogenic system. New zircon U-Pb and Sr-Nd-Pb isotope data and whole-rock geochemical analyses are presented on gabbroic to granitic rocks of the Chadormalu district to constrain the magmatic history of the Cadomian orogeny in a disrupted fragment of the northern Gondwana margin. The geochemical data identify I-type calc-alkaline magmatism with typical continental-arc features. The laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb zircon ages range from 531.1 ± 1.6 Ma to 539.8 ± 2.2 Ma, consistent with previous data on the Cadomian basement of Central Iran, and document Early Cambrian subduction and extension along northern Gondwana. Whole rock Sr-Nd isotope data for gabbro (ɛNdi= 0.4; i stands for initial; t = 533 Ma) and granites (ɛNdi= -3.6 to -3.0; t = 531–539 Ma) along with radiogenic Pb isotope data attest to melting of older continental crust triggered by mantle melts. The subduction regime was followed by slab retreat ± delamination in an extensional environment which allowed Ediacaran-early Cambrian flare up of magmatism along the northern Gondwana margin at a regional scale. [ABSTRACT FROM AUTHOR]

Uranium isotope ratios are reported for twenty‐nine geological reference materials (RMs) including igneous, metamorphic and sedimentary rocks, as well as sediments. Measurements were conducted on a multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS) using the 233U‐236U double spike technique. These RMs possess a wide range of matrices with U mass fractions ranging from 0.11 μg g‐1 to 18.7 μg g‐1. The δ234/238U values (relative to the n(234U)/n(238U) ratio at secular equilibrium) show minor fluctuations around the secular equilibrium value except for two Pleistocene speleothem RMs. The δ238/235U values (relative to the value for NBL CRM 112a (NBS SRM 960)) of igneous rocks and metamorphic rocks are within the range of the continental crust value (‐0.29 ± 0.03‰, 95% CI). The δ238/235U value for sedimentary rock and sediment RMs spans a wide range of 0.98‰, suggesting significant 238U/235U isotopic fractionation in low temperature environments. The range of δ238/235U RMs reported in this study (‐0.63‰ to 0.35‰) exceeds that of previous RMs (‐0.61‰ to 0.17‰), allowing inter‐laboratory calibration of wider ranges of geological and environmental samples. [ABSTRACT FROM AUTHOR]

In modern plate tectonic regimes, continental crust is generated above subduction zones in magmatic island arcs. Models for continental growth-largely based on the modeling of geochemical processes that can transform mantle melts into the intermediate composition of bulk continental crust-have been hampered by a lack of definitive geochronology, which could clarify the temporal emplacement of igneous rocks at the base of island arc crust. The Kohistan Arc Complex (KAC) of Pakistan is a rare window into a nearly complete section of lower arc crust, revealing a sequence of igneous rocks representing discrete batches of magma underplated along the base of the arc crust. We present high-precision isotope dilution-thermal ionization mass spectrometry U-Pb geochronological data from zircon, and Lu-Hf and Sm-Nd isochron data from several mafic lower crustal cumulates within the KAC. These data establish a clear downward-younging age trend throughout this succession of cumulate complexes, demonstrating a total magmatic duration of ~20 m.y., corresponding to a rate of lower crust formation of up to 200-260 km³ km-1 Ma-1. These results provide the first direct evidence of a sequential process of underplating, revealing a fundamental mechanism responsible for building the root of island arc crust. [ABSTRACT FROM AUTHOR]

Magmatic gas exsolving during late-stage cooling of shallow magmas has been considered an important facilitator of low-pressure alteration and metal transport. However, the chemical properties of such gas, particularly its metal transport mechanisms and capacity, remain elusive. Trace elements in minerals produced by gas-mediated surface reaction or precipitation from gas capture details of gas composition and reaction pathways. However, interpretation of mineral trace element contents is dependent on understanding crystallographic controls on gas/mineral partitioning. This work investigates the structural accommodation of As, Mn, Ga, Ge, Fe, and Ti in vapor-deposited topaz of vesicular topaz rhyolite from the Thomas Range, Utah, through single-crystal synchrotron microbeam X-ray techniques on picogram quantities of those trace elements. X-ray absorption near edge structure (XANES) data indicates that these elements are incorporated into topaz as As5+, Fe3+, Mn3+, Ti4+, Ga3+, and Ge4+. Extended X-ray absorption fine structure (EXAFS) analysis for these trace elements, compared to EXAFS of structural Al and Si, reveals that As5+ and Ge4+ are incorporated directly into the tetrahedral site of the topaz structure, with the octahedral site accommodating Mn3+, Fe3+, Ga3+, and Ti4+. For As5+ and Fe3+, the structural impact of substitution extends to at least second neighbors (other elements were only resolvable to first neighbors). Further interpretation of the EXAFS results suggests that the substitution of Ti4+ results in increased distortion of the octahedral site, while the other trace elements induce more uniform expansion correlating in magnitude to their ionic radius. Comparison of quantified X-ray fluorescence (XRF) data for two topaz crystals from this rhyolite reveals variable trace element concentrations for As5+, Fe3+, Ga3+, and Ti4+, reflective of a source gas undersaturated in these trace elements changing in concentration over the period of topaz deposition. The identical Ge4+ content of the two topaz crystals suggests that Ge4+ in the gas was buffered by the growth of another Ge4+-bearing phase, such as quartz. The very low Mn3+ content in the topaz crystals does not reflect the abundance of Mn3+ in the gas (saturation of Mn is evidenced by coexisting bixbyite). Instead, it suggests a strong Jahn-Teller inhibitory effect to the substitution of Mn3+ for Al3+ in the distorted octahedral site of topaz. It is proposed that exsolution of an HF-enriched gas from cooling rhyolitic magma led to local scouring of Al, Si, and trace metals from the magma. Once topaz crystals nucleated, self-catalyzed reactions that recycle HF led to continued growth of topaz. [ABSTRACT FROM AUTHOR]

Cenozoic potassic–ultrapotassic igneous rocks are widespread in the southeastern Tibetan Plateau. Their petrogenesis and magmatic processes remain subject to debate in spite of numerous publications. Almost all of the Cenozoic extrusive and intrusive rocks in the Yao'an area, western Yunnan Province, SW China, are geochemically shoshonitic, collectively termed here the Yao'an Shoshonitic Complex (YSC). The YSC is located in the (south) easternmost part of the ENE–WSW‐trending, ∼550 km‐long and ∼250 km‐wide Cenozoic magmatic zone; the latter separates the orthogonal and oblique collision belts of the India–Eurasia collision orogen. Previously published geochronological and thermochronological data revealed that the rocks of the YSC were emplaced over a short timespan of 34–32 Ma. This and our new data suggest that the primary magma of the YSC likely was formed by partial melting of ancient continental lithospheric mantle beneath the Yangtze Block. This part of the continental lithospheric mantle had likely not been modified by any oceanic subduction. Fractionation crystallization of an Mg‐ and Ca‐bearing mineral and Ti‐Fe oxides during the magmatic evolution probably account for the variable lithologies of the YSC. [ABSTRACT FROM AUTHOR]

The article focuses on responding to Hadlari's interpretation of the Fire Bay area in northern Ellesmere Island, Canada, which differs from Koch et al.'s conclusions. Topics include the rationale for changing the stratigraphic nomenclature, the significance of the Fire Bay fault, and a clarification of U–Pb zircon data, challenging Hadlari's assumptions and supporting Koch et al.'s proposed revisions to the geological framework.

The Songnan fault basin contains a significant distribution of basaltic volcanic rock structures, and serves as one of the primary types of reservoir in the area. Volcanic formations exhibit notable distinctions when compared to conventional oil and gas reservoirs, and the precise seismic response mechanism of these formations remains uncertain. Hence, it is imperative to investigate the seismic response mechanism of volcanic formations to enhance the geophysical characterization capability of oil and gas reservoirs composed of igneous rock. The seismic physical simulation model method is used to obtain dependable data for investigating the seismic response mechanisms of volcanic structures. This is achieved by constructing intricate physical models of rocks and volcanic structures. Our team focused on the development of materials and processes for accurately modeling various rock and volcanic structures, and we successfully designed and produced a three-dimensional physical model representing volcanic structures in the Chaganhua area. Furthermore, we conducted thorough data acquisition and analysis to examine the seismic response characteristics and sensitive properties of different geological bodies. We improved the accuracy of identifying different lithofacies of volcanic rocks by extracting different seismic attributes. This study presents a reliable approach for elucidating the seismic response mechanism of intricate rock and volcanic formations. It can also serve as a valuable resource for processing and interpreting seismic data in the specific study region. The conclusion that weak seismic reflection signals in volcanic rocks are effective signals rather than noise could be more conducive to accurate analysis and description of volcanic structures. [ABSTRACT FROM AUTHOR]

The Tennis Ball Marker (TBM) is a distinctive lithology that is particularly well developed near the base of the Rustenburg Layered Suite (RLS) on the farm Middelkraal 221 JS, approximately 20 km south of the town of Roossenekal in the Eastern Limb of the Bushveld Complex. The name refers to a texture in which approximately tennis ball-sized spheroidal aggregates of feldspathic orthopyroxenite or melanorite occur within a lighter-coloured gabbronorite host rock. We have identified two well-defined layers in which pyroxenitic spheroids are densely packed, with spheroids more sparsely distributed elsewhere in the host gabbronorite. The TBM at Middelkraal has previously been described as a contact phenomenon where the Main Zone (MZ) has been contaminated by footwall lithologies that include basaltic lavas of the Dullstroom Formation. Our geochemical data, in tandem with new geological mapping, suggest that the TBM is in fact hosted by the Marginal Sill Phase (MSP), and not by the MZ. The MSP is a regional feature that separates the overlying units of the RLS from its floor rocks throughout this region. Sills that make up the MSP were injected on a regional plane of weakness in the primary stratigraphy prior to the intrusion of the remainder of the RLS. The MSP does not represent the chilled carapace of a magma chamber, as implied in previous studies, and there is no evidence of a genetic relationship with the MZ. Our geochemical data indicate, furthermore, that the gabbronorite constituting the dominant lithology of the MSP that hosts the TBM at Middelkraal formed from a sequence of several magma influxes. The TBM is ascribed to one or more subsequent intrusions of pyroxenitic magma into the still hot gabbronoritic host sequence. There are no comparable lithologies reported from other layered intrusions, and the closest analogy to the TBM is the Boulder Bed in the Upper Critical Zone (UCZ) of the Western Bushveld Complex, which has received considerably more attention in the literature than has the TBM. The Boulder Bed has been ascribed variously to in-situ agglomeration of clusters of orthopyroxene resulting from liquid immiscibility, in situ breakup of a pre-existing pyroxenite layer, possibly due to seismic events, or the disaggregation of a late-stage pyroxenitic sill intruding into the magma chamber. We subscribe to the latter mechanism for both the TBM and the Boulder Bed, drawing on similarities with mafic magmatic enclaves, where mafic sills have been shown to have disaggregated on intrusion into earlier bodies of felsic to intermediate igneous rock, or peperites, where magma intruded fluidised sediments. [ABSTRACT FROM AUTHOR]

The undocumented Nkolkosse area belongs to the southern domain of the Pan African Fold Belt in Cameroon. Petrography and whole rock geochemistry reveal that the area is made up mainly of medium-grade gneiss of amphibolite facies. The mineral association in rock is quartz + potassic feldspar + plagioclase + biotite + muscovite ± rutile ± zircon ± opaque minerals. Their SiO2 contents are very high, varying from 76.37 to 80%, while the concentrations of Al2O3 are low (9.61–11.08%) and very low for CaO (< 1%). The average value of K2O/Na2O ratios is greater than 1 (1.40). All these characteristics point to metasedimentary rocks as revealed by the binary diagram TiO2 vs. SiO2, in which all the samples plot in the field of paragneiss. The inferred protoliths of Nkolkosse metasedimentary rocks yield the composition of arkoses and lithic arenites. These protoliths are from mature to immature sediments, resulting from chemical weathering of a felsic source and have experienced a high degree of sedimentary recycling, which supports the recycled nature of those meta-sediments with little contribution from igneous rocks. The protoliths of the Nkolkosse gneiss are from the upper continental crust and were deposited in a passive to active continental margin, within a subduction tectonic setting. These results are concomitant with other results described in the Central African Fold Belt in Cameroon, Brazil, and the northwestern edge of the Congo craton, inferring that they were forming a single block. [ABSTRACT FROM AUTHOR]

The effective exploitation of hydrocarbon from basement reservoirs requires an understanding of geomechanical parameters. Uniaxial compressive strength (UCS), Young's modulus (E), and Poisson's ratio (ν) are key attributes in addressing a range of geomechanical problems. The rock texture, which is chiefly dependent on the size, shape, orientation of grains, and their spatial distribution in the sample, provides valuable information about rock strength. In this study, we present the dependence of UCS on the rock texture in igneous and metamorphic basement rocks of western offshore India. A texture coefficient (TC) was calculated to quantify the rock texture, and an empirical relationship between TC and laboratory-derived UCS was standardized, which was then used to calculate UCS from TC. We also standardized new equations to calculate UCS from compressional (Vp) and shear wave (Vs) velocities using non-destructive technique (NDT). The static and dynamic values of E and ν were measured in laboratory, and new relations were standardized to calculate static from its dynamic equivalents. The results show that the dynamic values for ν are higher (approx. 22%) than the static values for all basement samples, whereas E exhibits a positive and a negative correlation between the dynamic and static values for mafic and felsic basement rocks, respectively. This study addresses the importance of rock texture in determining the UCS and the other associated elastic and geomechanical properties, which in turn will help in wellbore instability studies, planning hydrofracturing designs, and rock strength analysis of unconventional basement reservoirs of western offshore basin. [ABSTRACT FROM AUTHOR]

Distinguishing different kinds of igneous rocks is difficult because of their subtle differences. Synthetic aperture radar (SAR) is sensitive to rock surface morphology, which can help a lot in classification. Dual-pol SAR data have the advantages of low cost, but few articles are using only dual-pol SAR data for igneous rock classification. In this study, we explored the performance of dual-pol SAR data in distinguishing granitoid, tuff, and syenite porphyry. Backscatter coefficients, polarization decomposition parameters, and texture features from gray-level co-occurrence matrix extracted by Sentinel-1 or PALSAR were classified using several machine learning algorithms. The results are as follows. First, the texture information has greater potential for igneous rock classification, but the polarization decomposition parameters contribute less. Second, after comparing machine learning algorithms, AdaBoost algorithm has the highest overall accuracy for either C-band or L-band SAR data. C-band SAR data provide better classification results than L-band. Finally, tuff is the easiest igneous rock to be successfully classified, and L-band dual-pol SAR data have advantages in the discrimination of syenite porphyry. This study outlines the effectiveness of dual-pol SAR data for igneous rock classification, which will help to select SAR data of appropriate wavelengths for specific types of lithology discrimination.

The presence of oil accumulations in igneous rocks has been known for quite a long time. Geologists estimate that oil reserves in eruptive and weathered metamorphic rocks reach 1 % of the world’s proven oil reserves. At the Shaimskoye field (Western Siberia), oil is found in the weathered granites of the basement. Oil has been found in eruptive rocks in Texas (USA) fields, the most famous of which is the Litton Springs field. Oil is found in metamorphosed shales in the western part of the Los Angeles basin, the porosity of which is caused by the development of cracks in the roof of crystalline shales. Petroleum is extracted from serpentinites in Cuba. Basic igneous rocks contain petroleum at the Ferbro field in Mexico.At the Khukhrinsky gas field, which islocated at the north-western end of the Dnieper-Donets depression, the crystalline basement rocks are oil and gas bearing, from which commercial hydrocarbon inflows have been obtained. In the White Tiger field (Bach Ho), located on the southern shelf of Vietnam, commercial oil accumulations are also found in crystalline basement rocks. At the Muradkhanli field in Azerbaijan, the industrial accumulation of petroleum belongs to the igneous rocks of the Upper Cretaceous age. The natural oil and gas reservoir of the Muradkhanli field is confined to the erosion zone of the upper part of the section of these rocks. This work aims to determine the reservoir properties of the rocks of the Muradkhanli deposit, which belong to igneous rocks, in different ways. The method of estimation of final oil recovery of complex structure reservoirs was proposed for useful capacity and oil recovery of homogeneous media; different variants of the volumetric method were used for reservoirs with complex structures of pore space filling a complex and heterogeneous natural reservoir; values of hydrocarbon reserves of increased and secondary capacity were calculated for the study interval; distributions of oil reserves with right-sided asymmetry, where Mo

The Eastern Pontides in NE Turkey hosts a very limited number of plutonic rocks from the Jurassic period. Here we submit new geochemical, Sr-Nd-Pb and zircon Lu-Hf isotope data, and zircon U-Pb ages for plutonic rocks in this region. Zircon U-Pb dating for the Alemdar and Işıkdere plutons yielded an age of 175–170 Ma (Middle Jurassic). The Alemdar and Işıkdere plutons have I-type, medium to high-K calc-alkaline series, and metaluminous to slightly peraluminous characteristics. On PM-normalized diagrams, the plutons are enriched in large-ion lithophile elements (LILEs) with pronounced depletion of high field strength elements (HFSEs, Ta, Nb, Ti). Chondrite-normalized plots for the plutons show variable enrichment in light rare earth elements (LREEs) with depletion of heavy rare earth elements (HREEs). The rocks of the Alemdar Pluton have homogeneous ISr values (0.70585 to 0.70673), low εNd(i) values (−3.9 to −1.6), pozitif εHf(i) values (+3.3 to +9.1), and Hf single-stage model ages (563–712 Ma), whereas those of Işıkdere have high ISr values (0.70666 to 0.70673), low εNd(i) values (−3.9 to −3.8), εHf(i) values (−3.1 to +1.1), and Hf single-stage model ages (791–969 Ma). These values imply that they have different sources. These results suggest that the magma of the Alemdar was formed by the partial melting of a relatively depleted lithospheric mantle wedge interaction of the OIB-like melts, while those of Işıkdere have derived from the partial melting of an enriched mantle metasomatized by slab-derived sediments and then modified by fractional crystallization and crustal contamination in crustal magma chambers. Considering the available data, we conclude that the studied plutons were related to extensional tectonic events during the Middle Jurassic in response to the roll-back of the Paleotethys oceanic slab in the final stage of oceanic closure. These rocks are an example of the formation of deep subduction products following Early Jurassic subduction. [ABSTRACT FROM AUTHOR]

The results of investigations of the chemical and mineralogical composition and main characteristics are presented to determine the suitability of trachybasalt porphyrite of the Karabulak section of the Gavasai deposit in Uzbekistan for preparing thermal insulation material, in particular mineral fiber. It was found that this new deposit of igneous rock can be used as the main raw material component in the manufacture of basalt fiber products, a widely demanded and modern material in the construction industry. [ABSTRACT FROM AUTHOR]

Abstract—A number of examples are considered in which modern arkose sands as well as arkose and compositionally similar sandstones (all of the above rocks are sediments of the first sedimentation cycle) of different ages have definite provenances composed of granitoids of different "geodynamic" types. The main goal of the work is to analyze how the geochemical characteristics of granitoids are translated into petrogenic sedimentary rocks. The comparison of 245 analyses of sands and sandstones with ~375 analyses of the inferred prototype sources of clastic material showed that the lithogeochemical characteristics of arkose and subarkose sands and sandstones (mainly the HFS element content and ratio) makes it possible in most cases to confidently judge the "geodynamic nature" of source felsic igneous rocks. [ABSTRACT FROM AUTHOR]

There are four essential stress thresholds for the progressive failure of rock subjected to compressive loading, i.e., the peak strength (PS), crack damage stress (CD), crack initiation stress (CI) and crack closure stress (CC). Accurate values for these stress thresholds have important implications for rock mechanics and engineering geology. Here, first, current approaches for determining stress thresholds of rock were introduced and systematically reviewed. Subsequently, uniaxial compression was used in a series of laboratory tests on five common rocks including igneous, sedimentary and metamorphic rocks. Additionally, acoustic emission (AE) monitoring was conducted to analyse AE-based methods for determining the CI. The current methods were then compared. The pros and cons of these methods were discussed from the five perspectives of computational simplicity, solution stability, solution objectivity or uniqueness, clarity of physical meaning and universal applicability. The results showed two cases according to whether the volume strain curve had an inflection point. In both cases, the CD was calculated as the applied stress to the rock at the maximum volume strain. Among all ten methods, the lateral strain response (LSR) and the relative compression strain response (RCSR) were recommended for evaluating the CI. Among the five current methods, the compression coefficient response (CCR) was recommended to calculate the CC. The relationships between the CD, CI, CC and UCS values were strongly linear for different rocks. Ratios of stress thresholds for common brittle rocks, namely, CC/PS, CI/PS and CD/PS, were on average approximately 0.93, 0.60 and 0.17 based on the results of linear fits. These findings could be helpful in studies to select an appropriate approach for determining rock stress thresholds and, hence, to better evaluate the stability of rock-related engineering structures. Highlights: A comparison of current methods for determining rock stress thresholds was made from the five perspectives of computational simplicity, solution stability, solution objectivity, clarity of physical meaning and universal applicability. Regardless of whether the volume strain curve had an inflection point, the crack damage stress was calculated as the applied stress to the rock at the maximum volume strain. Among all ten methods, the lateral strain response and the relative compression strain response were recommended for evaluating the crack initiation stress. Among the five methods, the compression coefficient response was recommended to calculate the crack closure stress. [ABSTRACT FROM AUTHOR]

We report new experimental data from ultrabasic basanite and ultrabasic tephrite as starting material compositions in the 1350°C to 1000°C temperature range. Crystallization experiments under low- to high-pressure (0.5–2.0 GPa) were carried out under reduced conditions (≈CCO buffer), while one-atmosphere, anhydrous, experiments were performed ranging from reduced to oxidized conditions (−2 ≤ ∆QFM ≤ +2). The results highlight the ƒO2 role on the silica saturation of the alkali liquids differentiated from these primary ultrabasic magmas, on the mineral assemblage, and its composition. The liquid lines of descent (LLDs) from basanite are sodic and strongly SiO2 undersaturated, whereas from tephrite, the LLDs are sodic-potassic/potassic for both weakly SiO2-undersaturated and SiO2-saturated compositions, being more silica saturated under oxidized conditions. At the lowest temperature experiments, the percentage of liquid remaining is significantly higher in the basanite-derived products (ca. 35 wt.%) than in tephrite, indicating that the equivalent magmas are more prone to produce larger quantities of evolved melts. The best obtained Fe–Mg olivine/melt and clinopyroxene/melt exchange coefficients for these alkali compositions considering the new and available data are |${K_D}_{Fe^{2+}- Mg}^{Ol- Alkali\ melt}=0.285\pm 0.014$| and |${K_D}_{Fe^{2+}- Mg}^{Cpx- Alkali\ melt}=0.245\pm 0.008$|⁠ , slightly lower than those observed in tholeiitic melts. Clinopyroxene compositions are Ti–Al-rich and Si-poor as compared with common clinopyroxenes in subalkali systems. We suggest that Ti should be allocated in the tetrahedral sites substituting for Si and that its contents are inversely correlated with pressure. Our results allow a simple new barometer based on clinopyroxene-only compositions, as follows: $$ P\left(\pm 0.16\ GPa,1\sigma \right)=16.028\left(\pm 1.042\right) Na-6.715\left(\pm 0.727\right)\frac{Ti}{Ti+ Al(t)}+0.494\left(\pm 0.441\right) Si+0.144\left(\pm 0.079\right) $$ where Na, Ti, Al(t), and Si are molar proportions relative to 6O. This formulation accounts for the jadeite (NaAlSi2O6) component, herein computed from the Na contents, corrected for the Ti-diopside (CaMgTi2O6) component in clinopyroxene and also considers the evolutionary trend from Mg-augite to ferroan diopside. It applies to alkali ultrabasic to intermediate compositions in the examined P–T–ƒO2 range, resulting in more accurate estimates than the available calibrations. The MgO-in-melt thermometer was optimized for the studied compositions at one-atmosphere pressure and anhydrous conditions, as follows: $$ T\ \left(\pm 5{}^{\circ}C,1\sigma \right)=27.35\left(\pm 0.65\right)\ \big({MgO}^{liq}\big)+984\left(\pm 4\right) $$ which provides much more reliable liquidus temperatures for these alkali systems. Given data restriction, this formulation may be expanded to include the pressure effects for relatively low-H2O (< 3 wt.%) systems as: $$ T\ \left(\pm 20{}^{\circ}C,1\sigma \right)=27.35\left(\pm 0.65\right)\big({MgO}^{liq}\big)+80.20\left(\pm 5.50\right)P(GPa)+981\left(\pm 4\right) $$ [ABSTRACT FROM AUTHOR]

The reasons for the formation of rare minerals and mineral assemblages during metamorphism and metasomatosis are found to be the atypical composition of the protolith, the structural–textural heterogeneity, restricted mass transfer, and high temperatures. This is often observed under shallow conditions (pressure up to 3 kbar) during additional heating of rocks by igneous intrusions. In this paper, these questions are discussed with a series of domestic examples, the processes of mineral formation in which are studied in detail. [ABSTRACT FROM AUTHOR]

In the Kokchetav area, a late Neoproterozoic to early Palaeozoic metamorphic, ophiolitic, and volcanic–sedimentary complex provides important insights into crustal accretion in the northwestern Altaids. We carried out a systematic study of the Northern Complex in the mélange within the Chaglinka, Zhanatalap, and Chelkar regions. The mélange includes fragments of mafic igneous rocks, pelagic cherts, volcaniclastic rocks, and turbidites. The mafic rocks have high Mg#, Cr, and Ni values, small negative Nb–Ta anomalies, juvenile εNd(t)–εHf(t) values, and low 87Sr/86Sr(i) ratios, suggesting they were derived from a depleted mantle source in a supra-subduction zone setting. The volcaniclastic rocks exhibit moderate light rare earth element enrichment, small negative Nb–Ta anomalies, juvenile εNd(t)–εHf(t) values, and low 87Sr/86Sr(i) ratios, indicating they were derived from arc-related igneous rocks. The granites have features consistent with high-Sr/Y or A-type granites and variable εNd(t) and εHf(t) values, implying they formed by melting of arc-related volcanogenic sediments in the mélange. Zircon U–Pb ages for the volcaniclastic rocks vary from 540 to 423 Ma (Early Cambrian to late Silurian). These ages are consistent with those of volcanic rocks exposed in the Stepnyak–Selety arc. Subduction of the oceanic lithosphere beneath the Stepnyak–Selety arc may have occurred during the Early Cambrian and was followed by roll-back of the subducting slab during the Early Ordovician and continued subduction in the early Silurian. The successive subduction and accretion resulted in gradual maturation of the Stepnyak–Selety arc, which produced the compositionally and isotopically variable igneous rocks in the Kokchetav mélange zone and generated the juvenile crust of present-day northern Kazakhstan. [ABSTRACT FROM AUTHOR]

AG-MP-1M anion exchange resin is commonly used to separate and purify Cd from geological and environmental samples. However, a second column using anion exchange, TRU Spec, or BPHA extraction resins is also required to further purify Cd from the residual Sn for high-precision Cd isotope ratio measurements. In this study, a new and efficient single-stage separation method using AG-MP-1M (100–200 mesh) anion exchange resin was developed to separate Cd from geological and environmental samples for high-precision Cd isotope ratio measurements. Most of the Sn (>99%) is effectively stripped from the resin using a 2 M HCl + 4 M HF mixed eluent, unlike commonly used separation protocols with AG-MP-1M anion exchange resin, which only removes ∼65% of the Sn using HCl eluent. Furthermore, potential residual Sn is retained on the resin by elution of 0.04 M HCl + 2 M HF and 0.005 M HCl + 2 M HF, which allows quantitative collection of the Cd fraction (∼99.5%) without Sn tailing. The single-stage purification procedure takes advantage of the different affinities of Sn on AG-MP-1M anion exchange resin at different HCl and HF concentrations in mixed HCl + HF solutions, which allows direct and effective separation of Cd from Sn and other complex sample matrices. We used this procedure and the double-spike MC-ICP-MS method to determine the δ114/110CdNIST SRM 3108 values for Mn nodule, igneous rock, shale, soil, and sediment reference materials, and obtained results that agree within analytical uncertainty with the values reported in previous studies. In addition, the δ114/110CdNIST SRM 3108 values of soil (GSS-1a), sediment (GSD-4a), and dolomite (GSR-12) standard reference materials are reported for the first time in this paper. The described purification procedure allows efficient and rapid Cd isotopic analysis in different types of geological and environmental samples. [ABSTRACT FROM AUTHOR]

The East Kunlun Orogenic Belt (E-KOB) documents successive subduction and accretion processes of the Paleo-Tethyan Ocean. However, the tectonic regime of the E-KOB at the late orogenic stage remains ambiguous. This study presents new results of whole-rock geochemistry and zircon U-Pb-Hf isotopes of the Xidatan pluton in the southern E-KOB. Detailed investigation reveals that the pluton is composed of quartz monzodiorite, host monzogranite, and igneous microgranular enclaves (IMEs). Zircon U-Pb dating results suggest that they are coeval magmatic rocks emplaced at ca. 206–203 Ma. Geochemical studies reveal that the quartz monzodiorite and IMEs share a common magma source, evidenced by consistent compositions of major elements, congruently enriched LREEs and LILEs, and consistently moderately depleted HFSEs and HREEs. Enriched to slightly juvenile zircon Hf isotopes (εHf(t) = −4.24 to +0.49) indicate that the primitive magmas of the quartz monzodiorite and IMEs involve the addition of mantle-derived magmas. The quartz monzodiorite and IMEs have identical ages, and consistent isotope features with the host monzogranite, together with the observation of ingestion of xenocrysts from host felsic rocks into the IMEs indicating that they were produced through the mixing of the mantle-derived mafic magmas and host felsic magmas. In contrast, The host monzogranite has moderately high SiO2 and Na2O+K2O, but low Fe2O3T and MgO contents. It shows crust-like trace element patterns such as strong enrichments in LREEs and LILEs, but remarkable depletions in HREEs. Along with enriched zircon Hf isotopes (εHf(t) = −3.51 to −0.25), the host monzogranite was most likely to have originated from partial melting of lower crustal mafic rocks induced by underplated mantle-derived magmas. Considering abundant Late Triassic igneous rocks across the E-KOB, these new data provide further evidence that the Late Triassic magmatism in the E-KOB may be related to the delamination of thickened orogenic root under an extensional setting. [ABSTRACT FROM AUTHOR]

The Urumieh-Dokhtar magmatic arc (UDMA), Iran, hosts giant to small porphyry Cu ± Au deposits associated with Miocene post-collisional magmatism. Previous studies suggested that the ore-bearing suites are derived from chalcophile element-rich juvenile lower crustal igneous rocks, and that metal contents in the magmas play an important role in the formation of porphyry Cu ± Au deposits in this region. This study investigates the whole-rock major, trace, and platinum group element (PGE) geochemistry, as well as zircon trace element geochemistry, of six porphyry Cu ± Au ore-bearing suites and three barren suites in the central and southeastern UDMA. The aim is to revisit their petrogenesis and understand the factors controlling the formation of post-collisional porphyry Cu ± Au deposits. The high Mg# and Cr and Ni contents of the most mafic variants of ore-bearing and barren rocks suggest that they are primarily derived from the mantle. However, the ore-bearing magmas from the small Dalli Cu–Au porphyry and barren magmas from central to southeastern UDMA experienced substantial crustal assimilation during evolution. The evolved ore-bearing magmas exhibit high La/Yb and Sr/Y ratios, along with concave upward chondrite-normalized REE patterns and high zircon Ce/Nd and Eu/Eu* values, suggesting that they have undergone amphibole dominant differentiation under hydrous and oxidized conditions. In contrast, the barren magmas are characterized by lower whole-rock La/Yb and Sr/Y and zircon Ce/Nd and Eu/Eu* values with flatter REE patterns, implying plagioclase dominant differentiation. The ore-bearing suites, except for the Dalli suite, have systematically higher Pd and Pt contents than barren suites with highly fractionated PGE patterns (high Pd/Ir). The chalcophile element fertility of the ore-bearing suites, as indicated by high Pd/MgO and Pd/Pt ratios, is comparable to that observed in porphyry Cu deposits found elsewhere. This similarity suggests that the Cu contents of the magma likely played acrucial role in the formation of the porphyry Cu deposits in the central and southeastern UDMA. Late sulfide saturation or small amounts of sulfide segregation may have led to the high Cu and moderate Pd contents of the ore-bearing magmas until the late stage of differentiation. In contrast, early sulfide saturation resulted in significant depletion in all PGE and Cu in the barren magma. The fractionated PGE patterns of the ore-bearing magmas could have arisen due to two potential processes. Firstly, they may have resulted from fractional crystallization of Cr-spinel in the early sulfide undersaturated differentiation. Secondly, the patterns might have been inherited from partial melting of metasomatized lithospheric mantle. The systematic geochemical differences between ore-bearing and barren suites suggest that the more hydrous and oxidized nature and higher Cu contents of the ore-bearing magmas substantially increase the porphyry Cu ore potential in the central and southeastern UDMA. [ABSTRACT FROM AUTHOR]

In the Mississippian Matachel small volcanic field of the Ossa-Morena Zone (southern Iberian Massif) outpoured basic-intermediate lavas exhibit geochemical characteristics of Low-Ti continental tholeiites and calc-alkaline lavas. Low-Ti continental tholeiites integrate two contrasting groups of rocks: basalts (Mg#: 54 to 70; Ti/Zr: 61-79; LaN/LuN: 1.6-2.9; εNdi: +4.0-+6.6; "Group #1"), and basalts and basaltic andesites (Mg#: 43 to 66; Ti/Zr: 36-58; LaN/LuN: 2.5-5.9; εNdi: -0.2-+3.5; "Group #2"). Primitive Group #1 tholeiitic magmas were generated by partial melting of a garnet-free lherzolite from an enriched lithospheric mantle, near the lithosphere-asthenosphere thermal boundary layer (with a very limited asthenosphere melting input). Progressive interaction of these magmas with crustal alkali igneous rocks resulted in the formation of the petrological evolutionary trends observed, to a larger extent in the case of Group #2 Low-Ti tholeiites. Further assimilation of amphibole-rich calc-alkaline metaigneous rocks might have originated the basalts and basaltic andesites with calc-alkaline signature (Mg#: 33 to 56; Ti/Zr: 25-78; LaN/LuN: 2.0-5.6; εNdi: +2.8-+4.8). These exhibit a "Cordilleran-type" evolutionary trend, though are unrelated to plate convergence. The magmas with calc-alkaline signature attest to a closed-system differentiation process controlled by the fractionation of plagioclase, clinopyroxene, magnetite and ilmenite. It is proposed that Mississippian lithospheric-scale intra-continental wrenching, unrelated to coeval mantle plume upwelling, reworked complexly docked mantle domains and triggered mantle melting. Enduring mid-upper crustal processes (magma storage in mid-crustal chambers and crustal assimilation) likely shaped the latest petrologic and geochemical aspects of the Matachel Low-Ti tholeiites and related rocks with calc-alkaline signature. [ABSTRACT FROM AUTHOR]

Igneous rocks associated with the Cretaceous to Paleogene volcanic arc in SW Japan show ages that young from west to east in a direction parallel to the Median Tectonic Line suggesting corresponding translation of a heat source traditionally interpreted in terms of oblique subduction of a spreading ridge. However, recent oceanic plate reconstructions suggest ridge subduction may be younger than the main arc activity. Age compilations of 1227 points of felsic to intermediate Cretaceous and Cenozoic igneous rocks from the Japan arc show arc magmatism that can be separated into an early active period 130–60 Ma (stage 1), a subsequent period of quiescence 60–46 Ma (stage 2), which is followed by a resumption of igneous activity from 46 Ma onward (stage 3). In southwest Japan, the orientations of the magmatic arcs of stages 1 and 3 show and angular discordance of about 20°. The lack of active arc magmatism and the occurrence patterns of adakitic and high-Mg andesitic magmas indicate that ridge subduction occurred during stage 2. The arc age distribution pattern of stage 1 is explained by the slab shallowing related to a younging of the subducting slab as the ridge approaches. Furthermore, the obliquity of the arcs formed at stages 1 and 3 is explained by a 20° clockwise rotation of the inner zone of southwest Japan during the ridge-subduction phase. Oceanic plate reconstructions show counterclockwise rotation in the subduction direction after the ridge subduction phase, and coupling of the subducting oceanic plate with the upper plate would support microplate rotation in the inner zone. The new proposed tectonic reconstructions provide a framework to related Paleogene subduction of an active spreading ridge along the east Asia margin not only to the distribution of granitic bodies but also to rift-related basin formation on the eastern margin of the Eurasian continent and to rotation of crustal blocks indicated by paleomagnetic data of Cretaceous terranes. [ABSTRACT FROM AUTHOR]

New data on the geological position, U‒Pb SIMS zircon ages, petrogeochemical features, Sr‒Nd isotopic composition, and geodynamic setting of the granitoids and volcanics of the Northern volcanic-plutonic belt of the Verkhoyan–Kolyma fold area are presented. Magmatic rocks of the belt include granitoids of Elikchan, Kuranakh, and Bakyn plutons, composed of Elikchan granite–granodiorite complex and volcanics of predominantly intermediate-felsic Tumusskaya sequence with subvolcanic bodies of the same composition. They form a single Early Cretaceous (127–121 Ma) volcanic-plutonic assemblage. Granitoid plutons are elongated in a sublatitudinal and northwestern direction and are discordant to main fold-and-thrust structures. Granitoids intrude and metamorphose Jurassic terrigenous and Early Cretaceous volcanics of Tumusskaya sequence and are intruded by younger Late Cretaceous subvolcanic bodies. Granitoids of Bakyn, Elikchan, and Kuranakh plutons combine petrogeochemical features of I-, S-, and A-type granites. Such diversity of petrogeochemical granitoid types, as well as interrelations of major ( –TiO2–MgO) and rare (Ba/La–Nb × 5–Yb × 10) elements in granitoids and the same age volcanics of the Tumusskaya sequence, allow us to refer them to igneous rocks of transform or sliding plate boundaries. Collision between the Chukotka microcontinent and the Siberian continent with the earlier accreted Kolyma–Omolon microcontinent in Barremian–Aptian time changed to postcollisional extension and formation of volcanic-plutonic assemblage of the Northern volcanic-plutonic belt. Postcollisional extension took place at the transform or sliding plate boundaries. Sr–Nd isotopic characteristics of granitoids of all granite plutons indicate the interrelation of mantle and crustal sources of granitoid melts in this process. [ABSTRACT FROM AUTHOR]

The results of mineralogical and geochemical studies of sandstones and siltstones of the Ernichnaya Formation of the Argun Series of the Argun continental massif and the U–Pb (LA-ICP-MS) age of their detrital zircon are presented. It is found that the youngest group of detrital zircon has the age of 549–570 Ma with a maximum on the probability density curve of zircon ages of 566 Ma. This suggests that the lower age boundary of their accumulation corresponds to the Ediacaran–Paleozoic boundary. According to the results of U–Pb (LA-ICP-MS) dating of zircon grains, the dominant zircons in sandstones of the sequence have Neo- and Paleoproterozoic ages. These zircons were probably sourced from the Neo- and Paleoproterozoic igneous and metamorphic rocks widely abundant within the Argun continental massif. The geochemical features of terrigenous rocks of the sequence together with the presence of poorly sorted and weakly rounded rock clasts in the studied samples, as well as the presence of interlayers of gravelites in structure of the sequence, indicate their accumulation in a subduction-related setting. [ABSTRACT FROM AUTHOR]

The results of U–Th–Pb (LA-ICP-MS) geochronological studies of detrital zircon and Sm–Nd isotopic studies of metaterrigenous rocks of the Udokan Complex of the Nizhnekhani graben-syncline in the western part of the Aldan Shield are discussed. On the basis of the data obtained, it was found that the accumulation of terrigenous deposits of the Nizhnekhani graben-syncline occurred after 2.65 and up to 1.9 Ga, probably at the Paleoproterozoic stage of the development of the region. The igneous and metamorphic rocks formed at ca. 2.65, 2.71, 2.82–2.86, 2.99, 3.10–3.21, and probably 3.26–3.42 Ga within the Chara–Olekma Geoblock, its junction zone with the West Aldan Megablock, and the Kurulta Block of the Stanovoi suture zone were the sources of detrital material. Metaterrigenous rocks of the Nizhnekhani graben-syncline were formed from crustal sources with the Paleo- and Mesoarchean Nd model ages, while a significant contribution of the Paleoproterozoic juvenile material was established for the metasedimentary rocks of the Kodar–Udokan Trough. Significant differences in the age and Nd isotopic characteristics of sources of terrigenous deposit of the Nizhnekhani graben-syncline and the Kodar–Udokan Trough suggest that they accumulated in isolated basins. [ABSTRACT FROM AUTHOR]

The Adria-derived Drina-Ivanjica Unit of the Internal Dinarides represents a composite basement-cover thrust sheet passively carrying obducted Jurassic ophiolites and post-obduction Upper Cretaceous sedimentary rocks, penetrated by post-orogenic Miocene igneous rocks. This study presents the first paleomagnetic results from the Drina-Ivanjica Unit obtained at a total of 34 geographically distributed localities, representing Triassic-Jurassic carbonates, Upper Cretaceous carbonate and flysch successions, as well as Miocene igneous rocks. Paleomagnetic directions for the igneous rocks and the Upper Cretaceous flysch, which had clearly remagnetized during Miocene magmatism, point to a 30° clockwise (CW) rotation, which must have taken place after 20 Ma. This angle perfectly agrees with the earlier-published value for both the Western and Eastern Vardar zones (including the Jadar-Kopaonik thrust sheet, the Sava Zone, and the Cretaceous overstepping sequence of the Eastern Vardar ophiolitic unit), suggesting a coordinated rotation between them and the Drina-Ivanjica Unit. Results of the present study set a younger age constraint (20 Ma) for the commencement of the coordinated CW rotation instead of the previously suggested 23 Ma. The rotation may have connected to the extension induced by the slab rollback of the Carpathians, which was also responsible for the opening of the Pannonian Basin. The paleomagnetic directions for the Cenomanian-Turonian carbonates, which are situated far from the magmatic bodies, are interpreted in terms of a minor counter-clockwise (CCW) rotation taking place before the Miocene CW rotation. The Triassic-Jurassic carbonates of the Drina-Ivanjica Unit have post-tilting magnetizations, which were likely induced by the thermal effect of the obducted ophiolites. The overall mean paleomagnetic direction suggests a rotation of about 50° CCW between 150-20 Ma, which is in line with the well-documented post-150 Ma CCW rotation of the Adriatic microplate. [ABSTRACT FROM AUTHOR]

Melt percolation through partially molten "mushy" regions of the crust underpins models for magma migration, accumulation, and processes that prime systems for eruption. Knowledge of the hydraulic properties of magma mush, specifically permeability, is required for accurate predictions of melt migration rates and accumulation timescales. Previous studies, validated for cuboidal crystal analogs, show that crystal shape exerts a first‐order control on the permeability, and is tested here for anisometric natural crystal shapes using X‐ray CT 3D data sets of magma mush analogs made from packed confectionary particles arranged randomly. We use a lattice‐Boltzmann fluid flow simulation tool to determine the permeability of the analogue melt phase network between the packed particles. We find excellent agreement with our data sets to within ∼0.1 log units, when the specific surface area is measured. To extend this to more typical cases where the specific surface area is unknown, we use the shape and size of the objects determined in both 3D and 2D to estimate the specific surface area assuming a cuboid approximation. These approximate solutions give good results to within ∼0.5 log units of the measured permeability and offer a method by which permeability could be estimated from a thin section of a cumulate or pluton sample. Our shape‐sensitive approach is more accurate than existing models for permeability of magma mush, most approximating natural crystal shapes to spheres. We therefore propose that these could be implemented in dynamic magma mush models for melt movement in the crust to produce more accurate flux predictions. Plain Language Summary: Magma chambers in the Earth are "mushy," meaning that liquid magma is trapped in between solid crystals. In many cases, the liquid magma must escape before an eruption occurs. For the liquid magma to escape, it must move through the tight spaces between the solid crystals, which occurs at a speed dictated by the "permeability" of the crystal framework. Here, we use fudge and sugar crystals as a proxy for the solid crystals in these magma chambers, and we use simulations to observe how the fluid between the fudge and sugar moves. The key advance here is that we show how the complicated shape of fudge and sugar crystals changes the speed at which the fluid is able to move. Key Points: Crystal shape exerts a first order control on magma mush permeabilityThe specific surface area of magmatic crystals is the relevant metric to predict the permeability, across all crystal shapesMagma mush permeability can be calculated from crystal size measurements made on a 2D thin section, via a 2D‐to‐3D conversion [ABSTRACT FROM AUTHOR]

A suite of subduction-related early Triassic igneous rocks crops out in the Pingxiang area of the DianQiong suture (DQS) in southwest China; this suite represents an important geological record of subduction and closure of the Paleo-Tethys Ocean. In this study, we report geochronological, geochemical, and NdHf isotope data for newly discovered rhyolites and biotite granites in the Pingxiang area. We use these data to constrain their emplacement ages, origins, and geodynamic implications. Zircon U-Pb dating indicates that the rhyolites and biotite granites were emplaced at 251–250 Ma and 249 Ma (early Triassic), respectively. The rhyolites and biotite granites have elevated FeOT/(FeOT + MgO) (0.78–0.89) and 10,000 × Ga/Al (2.83–4.11) ratios, with geochemical affinities to A2-type granites. These rocks are enriched in some large-ion lithophile elements (e.g., Rb, Th, and Ba) and depleted in high-field-strength elements (e.g., Nb, Ta, and Ti), indicating their formation in a subduction-related arc. The rhyolites and biotite granites have negative whole-rock εNd(t) (−11.5 to −9.7) and zircon εHf(t) (−14.5 to −6.2) values, suggesting that these magmas were derived from an ancient crust-dominated source. Geochemical and Nd isotope data reveal that the peraluminous A2-type rhyolites and biotite granites were derived by partial melting of felsic crustal rocks under low-pressure and high-temperature conditions. By integrating all the available data with the regional tectonic evolution of the southwestern Youjiang Basin and adjacent regions, we attribute the generation of the peraluminous A2-type rhyolites and biotite granites to the extensional setting that existed during oceanic subduction, which was induced by roll-back of the Paleo-Tethys oceanic lithosphere at 251–249 Ma. This study indicates that subduction-related magmatism related to Paleo-Tethys oceanic lithosphere was still active in the early Triassic. [ABSTRACT FROM AUTHOR]

This paper considers the results of the mineralogical and chemical study of sandstones and U–Pb isotope dating of detrital zircons from the Paleozoic–Early Mesozoic deposits of the Laoeling–Grodekovo terrane in western Primorye. It is shown that the sandstones of different age of the terrane differ markedly in their mineralogical and geochemical parameters and, hence, were derived from different sources. The sandstones of the Kordonka Formation are made up of fragments of basic and intermediate volcanic rocks of the oceanic island arc, as well as igneous and sedimentary rock associations of the oceanic island-arc basement. Eroded stable cratons and uplifted blocks representing crystalline basement inliers that are either flanked by rift zones or occurring along transform faults exerted a strong effect on the accumulation of sandstones of the Reshetnikovka, Barabash and Mangugai formations. The main suppliers of detritus were felsic igneous rocks with minor input from ancient sedimentary rocks. The rift margins and the eroded ensialic arc provided clastic material for the rocks of the Talmi Formation. The U–Pb geochronological studies of detrital zircons made it possible to constrain the age and possible position of igneous complexes that supplied clastic material to the sedimentary basins of the terrane. The sandstones were found to contain detrital zircons with concordant ages from 2553 to 205 Ma, which are dominated by Paleozoic zircons divided into several age groups. The zircons of Precambrian and Triassic ages are far fewer. In general, the revealed age ranges of detrital zircons from sandstones of the Laoeling–Grodekovo terrane agree fairly well with the known stages of granitoid magmatism in the eastern part of the Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The U(Pb)-Pb age of zircon is commonly used to represent the crystallization age for igneous rocks due to its high closure temperature and robust resistance to impact disturbance. However, no zircon crystallization age has yet been reported for Chang'e-5 (CE-5) basalt due to their limited occurrence in mare basalt. In this study, rare zircon grains from CE-5 lunar samples were investigated by the in-situ Pb isotopic analysis, and a precise zircon crystallization age of 2036 ± 19 Ma was determined from Pb-Pb isochron. This is hitherto the youngest reported crystallization age of lunar zircon, similar to the ages of CE-5 lunar basalts obtained by zirconium (Zr)-bearing minerals such as baddeleyite, tranquillityite, and zirconolite. Petrographic evidence and rare-earth element geochemistry indicate that zircon in the CE-5 lunar basalts were formed by the reaction of early-formed baddeleyite with SiO 2 melt within the latest residue of extreme fractionation of a non-KREEP (an acronym for potassium, REE, and phosphorus) basaltic magma. In contrast to the prevailing view that lunar zircon have formed in late-stage enriched melts resulting from extensive fractional crystallization of the Lunar Magma Ocean, this study shows that zircon could be derived from extreme fractionation of non-KREEP basaltic magma unrelated to Lunar Magma Ocean. [ABSTRACT FROM AUTHOR]

Gabbroic and microgabbroic shergottites are intrusive igneous rocks on Mars and exhibit a wide variety of mineralogical and geochemical properties. However, their source reservoirs, magmatic processes and the link to other shergottite subtypes are not well constrained. Northwest Africa (NWA) 13581 is a newly found permafic olivine gabbro, representing a cumulate member in the shergottite group. This sample provides new critical constraints on the characteristics of mantle sources and magmatic evolution of shergottites. The texture and mineral chemistry of NWA 13581 indicate a polybaric crystallization condition, with an increase in oxygen fugacity of approximately 1 log unit after ascent and emplacement. Geochemical studies suggest that the sample is young (150 ± 25 Ma) and may share a similar enriched mantle reservoir (initial ε176Hf i = −18.4, initial ε143Nd i = −7.1) with shergottites like Zagami (basaltic shergottite), NWA 10169 (poikilitic shergottite) and Larkman Nunatak 06319 (olivine-phyric shergottite). In addition, the presence of potassium-rich melt inclusions enclosed in early-formed minerals of NWA 13581 implies a fertile source, probably originating from a metasomatized mantle. The occurrence of similar potassium-rich components in other enriched shergottites may suggest a common process in their mantle reservoir and during crystallization. Overall, NWA 13581 resembles poikilitic shergottites closer than typical gabbroic shergottites in several aspects such as poikilitic texture, mineral chemistry, magmatic evolutionary path, and emplacement conditions. A simplified model is proposed for the formation of NWA 13581 and poikilitic shergottites in the same magma series. Magma mixing and/or assimilation are not the major mechanism that account for their slightly varied mineral modal abundances and quantitative textural characteristics. For samples derived from similar mantle sources, the textural and mineralogical diversities of shergottites are largely related to crystallization at different crustal levels. [ABSTRACT FROM AUTHOR]

This article presents data on the composition of biotite from igneous rocks of the Shakhtama complex, which are associated with various types of mineralization in Eastern Transbaikalia: Au-Cu-Fe-skarn, skarn-porphyry, Mo-porphyry, rare-metal–greisen, Au-polymetallic and Au-Bi. The major element and halogen contents were determined by EPMA. The content of trace elements was determined by means of LA-ICP-MS. As a result, the specific traits of the composition of the biotite of igneous rocks associated with specific types of mineralization of the Eastern Transbaikalia were determined. The biotites of rare-metal–greisen deposits are characterized by the maximum content of fluorine (>2 wt. %) and low chlorine content (<0.04 wt. %). In addition, such biotites are characterized by high XFe (>0.47). Within Eastern Transbaikalia, igneous rocks developed at the Bystrinsky deposit are potentially ore-bearing for the "classic" porphyry type of mineralization. They have the highest values of IV(F/Cl) (4.9–7.1) and IV(F) (2–2.8) and the lowest values of Log(XMg/XFe) (0.1–0.4). The trace element composition clearly distinguishes biotites from rare-metal–greisen deposits and is identified by the highest contents (ppm) Ga > 65, Li > 600, Sn > 20, Mn > 2000, Cs > 50, Zn > 600. Biotites of Au-polymetallic and Au-Bi deposits occupy an average position between rare-metal–greisen and Mo-porphyry ones. Biotites of Mo-porphyry deposits differ in minimum values (ppm) of Sn < 3, Zn < 160, and low values of Li (150–290), V (290–440), and Ga (39–48). In general, the chemical composition of biotites shows that the degree of igneous rock fractionation of deposits increases in the series: porphyry–skarn–polymetallic–rare-metal. [ABSTRACT FROM AUTHOR]

The assembly and break-up of supercontinents have been hot research topics in international earth sciences because they represent a breakthrough in reconstructing the history of continental evolution and deepening the theory of plate tectonics, which is of indispensable importance to the development of earth sciences. With the continuous enrichment of paleomagnetic, paleontological, chronological, and geochemical data in the last two decades, the evolution of the supercontinent from Columbia to Rodinia has gradually gained unified understanding, and the reconstruction of the major plates within the supercontinent has basically been constrained. In contrast, the reconstruction of microplates, such as South China, Tarim, and Kabul, is controversial and has now become a popular topic and frontier area of supercontinent reconstruction. Hainan lies at the southern tip of South China, and a few Proterozoic units are exposed on the island. At present, Hainan is often taken as a part of the Cathaysia Block. However, due to the lack of exposed Mesoproterozoic igneous and supercrustal rocks in Cathaysia, the reconstruction model of the Cathaysia Block and even the South China Craton based solely on Mesoproterozoic units in Hainan are distinct from those based on units in the Yangtze Block and younger Proterozoic units within the Cathaysia Block, which makes the paleoposition of the South China Craton controversial. In this paper, we provide new detrital zircon U–Pb age data for the Baoban Complex, Hainan, together with the available data to comment on the affinities between Hainan and the Yangtze and Cathaysia Blocks in the Proterozoic, and on this basis, we can reconstruct the South China Craton within the Proterozoic supercontinents. [ABSTRACT FROM AUTHOR]

Saidenbachite started to crystallize from melt under ultrahigh pressure (UHP). This felsic igneous rock is known from two occurrences in the world only. The here reported new type of saidenbachite, found at the type locality in the central Erzgebirge Crystalline Complex, is characterized by millimetre‐sized aggregates of coarse‐grained quartz in a matrix of significantly smaller grains of garnet, rarely containing diamond inclusions, plagioclase, K‐feldspar, white mica, some dark mica, rutile and ±kyanite. According to the shape and the regular distribution of these aggregates showing similar size, they are interpreted as former coesite phenocrysts, which grew early in a felsic magma. This interpretation is corroborated by thermodynamic modelling demonstrating that coesite is the first major phase that crystallizes from SiO2‐rich (>66 wt%) magmas at UHP. [ABSTRACT FROM AUTHOR]

The genesis of giant gold provinces is an international scientific frontier, in which the source of a huge amount of gold and the drive for mineralization are key challenges. The mineralization intensity of the Jiaodong gold province in eastern China is a rare occasion in the world, because it owns gold reserves of ∼5500 tons within an area of less than 10,000 km2. The Jiaodong gold province formed in the superimposed domain of diverse tectonic regimes in an intracontinental setting. Paleoproterozoic regional peak metamorphism and Triassic continental collision are followed by the tectonic transition and gold mineralization at ca. 120 Ma with time intervals of 1.9 billion years and about 100 million years, respectively. The Jiaodong gold deposits are different from orogenic and intrusion-related gold deposits in terms of the tectonic background, types of host rocks, and ore-forming mechanism. These gold deposits show close spatial-temporal and genetic relationships to mafic igneous rocks, implying the derivation of ore-forming fluids from the metasomatic mantle domains. Mafic dykes in Jiaodong have negative εHf(t) values of −29.9 to −9.1, Os content of 0.002–0.16 ppb, heavy δ18O up to 8.23‰, and high initial 187Os/188Os ratios of 0.1352–0.8858. These indicate that the lithospheric mantle was metasomatized by ancient crust-derived components. The lithospheric mantle in the western Jiaodong shows generally more enriched isotope features than that in the eastern part, which is explained to be an important reason for its huge gold resources. The mafic dykes show lighter Mg isotope characteristics (average δ26Mg of −0.33‰, n=50) and high CaO content (overall greater than 6.5 wt%), indicating that the lithospheric mantle would also record the metasomatism by the carbonate rocks from the subducting oceanic slab. Under the background of the rollback of the subducting paleo-Pacific slab and the destruction of the North China Craton, partial melting of the lower crust would produce granitic magmas that led to the enrichment of gold in the residual crust. The syn-mineralization asthenosphere upwelling would promote the recycling of the lower crust and the partial melting of the metasomatic mantle domains. Basic magmas, produced by the partial melting, and the mantle itself would degas to form ore fluids. The ore fluids would further leach gold in the lower crust to increase its fertility. The auriferous fluids were transported to the middle to upper crust along the detachment and strike-slip faults. Water-rock interaction and fluid immiscibility, which occurred in and above the ductile-brittle transition zone to induce gold precipitation, formed the Jiaodong gold deposits. Given the unique geological features and genetic model of the Jiaodong gold deposits, they can be defined as "Jiaodong-type" gold deposits. [ABSTRACT FROM AUTHOR]