Quartz Monzonite Research Articles

Petrology and Geochemistry of Intrusive Rocks in the Tanjung Area, South Sulawesi, Indonesia: Implications for Magma Origin, Source Materials, and Geodynamic Setting

The origin of magma, source materials, and geodynamic setting of plutonic and volcanic rocks was elucidated by studying the characteristics of the rocks in the Tanjung area, South Sulawesi, Indonesia. The composition of plutonic rocks is dominated by granodiorite, granite, monzonite, and quartz monzonite, whereas volcanic rocks consist of porphyry basalt, amygdaloidal basalt, trachyte, and trachy-andesite. The main minerals in the rocks are quartz, K-feldspar plagioclase feldspars, Hornblende, biotite, pyroxene, and some opaque minerals. Plots of plutonic rock samples with calc-alkaline affinity indicated a typical I-type granitic rock. Meanwhile, plots of volcanic rock samples with calc-alkaline to shoshonitic affinity indicated S- and I-type basaltic rocks. Harker diagrams suggested that the rocks underwent crystallisation fractionation during magma evolution. Plutonic and Volcanic rocks showed enrichment of LILE and LREE and negative Eu anomalies, which resemble continental crust affinity. It is a product of partial melting in the upper continental crust. The geochemical characteristics demonstrate the relationship between the subduction environment and a continental arc.

Late Paleozoic potassic igneous rocks of the Adyrtor intrusions in the eastern Kyrgyz Tien Shan: geochemistry, isotope U-Pb zircon geochronology, and related W-Mo(-Cu-Au) mineralization

ABSTRACT The Adyrtor multiphase pluton is situated in the easternmost part of the ‘Main Structural Line of Tien Shan’, or the ‘Nikolaev Line’, and intrudes the Paleoproterozoic metamorphic sequence representing the oldest (1.8–2.5 Ga) continental basement fragment in the Tien Shan orogenic belt. The intrusions comprise mafic to intermediate (monzodiorite, monzonite, quartz syenite) and silicic (quartz monzonite, monzogranite, and leucogranite-alaskite) rocks. Geochemical signatures of the igneous rocks correspond to high-K calc-alkaline to shoshonitic series intrusions, with a strong A-type granite affinity, emplaced in post-collisional setting. Based on the isotopic U-Pb data, quartz syenite from the Adyrtor intrusions crystallized at 330.7 ± 4.3 Ma, and quartz monzonite – at 329.5 ± 5.8 Ma. Although the ages identified correspond to those of the subduction-related magmatism in the western part of the Middle Tien Shan, geochemical characteristics of the rocks support rather post-collisional setting of the plutons, principally due to a ‘scissor-like’ closure of the Turkestan paleoocean, starting from the east. Magmatic evolution included a generation of shoshonitic magma by low-degree partial melting of the metasomatically-enriched upper mantle, followed by amphibole fractionation in a deep (lower crustal ?) magma chamber. Then, under the influence of mantle-supplied fluids and heat, granitic magmas in the crustal protolith could have been generated, with further mixing/mingling of the mantle-derived mafic (shoshonitic) magma and mantle-induced crustal granitic magma, followed by the magma fractionation and emplacement at shallower crustal levels. Assimilation of an old continental crust is also envisioned, consistent with the presence of the xenocrystic zircons dated at ca. 1.6 Ga to 2.5 Ga and the A-type granitoid affinity of the igneous rocks. The associated skarn-porphyry W-Mo(-Cu-Au) mineralization is consistent with post-collisional setting of the productive intrusions. This mineralization complements the group of similar deposits and occurrences associated with high-K calc-alkaline to shoshonitic series intrusions in the Middle Tien Shan and globally. The high endowment in W and Mo can be explained by the fertilization of subduction-modified subcontinental lithospheric mantle in these metals, with its further involvement in the magma generation in post-collisional setting. Also, a stronger W-Mo mineralization can reflect a greater role of a crustal protolith in the magma generation, as revealed by the distinct A-type affinity of the igneous rocks.

Multistage mineralizing episodes of the Proterozoic world-class Volta Grande gold deposit, Amazonian Craton, northern Brazil: Implications for the Bacajá Domain metallogenesis

The easternmost region of the Amazonian Craton in northern Brazil has been the focus of several mining exploration surveys, which led to the identification of the world-class Volta Grande gold deposit (∼6.0 Moz@1.02 g/t). The deposit is inserted in the Bacajá Domain (2.24–2.0 Ga), and part of the mineralization occurs in Proterozoic mylonite, gneiss, and associated metamafic rocks that underwent greenschist to amphibolite-facies metamorphism. Electrum (Au–Ag) occurs as grains in cm-sized quartz high-grade veins and veinlets (up to 34.1 g/t in some rock intervals) that follow the mylonitic foliation and are associated with pervasive carbonate alteration, synchronous with the dynamic metamorphism. Disseminated electrum grains, pyrite, chalcopyrite, arsenopyrite, tellurides, and galena occur associated with potassic, argillic, propylitic, and silicic alteration types mainly in fracture-controlled or pervasive styles. These geological features as a whole suggest an orogenic high-tonnage orogenic gold system. Isotropic core samples along a stratigraphic profile reveal late andesite, dacite, rhyodacite, and rhyolite lava flows and dikes and plutonic rocks such as quartz monzonite, granodiorite, monzodiorite, and subordinate microgranite crosscutting the older metamorphic rocks. These rocks reveal potassic, propylitic, argillic, silicic, and sericitic alteration types. Electrum grains, possibly related to boiling deposition, occur along cm-sized quartz, calcite, and adularia high-grade veins (up to 29.5 g/t in some rock intervals) with chalcopyrite, pyrite, arsenopyrite, tetradymite, and tellurobismuthite. Such mineralogy is compatible with a low-sulfidation epithermal system. Data integration points to at least two distinct mineralizing events leading to the Volta Grande gold deposit – orogenic gold and low-sulfidation epithermal – which explains such large-tonnage and high-grade ore accumulation. It configures a new exploration guide for the Bacajá Domain of the Amazonian Craton, attested by other worldwide regions with similar metamorphic, magmatic, and hydrothermal alteration characteristics.

Post-collisional magmatism and local lithospheric thinning in the Neoproterozoic Alto Pajeú Domain, northeastern Brazil: Geochemical and isotopic evidence

The 595–560 Ma post-collisional magmatism in the Alto Pajeú Domain, Borborema Province, northeastern Brazil, is characterized by the intrusion of voluminous high-K calc-alkaline, shoshonitic and ultrapotassic magmas. The nature of the source rocks and the geodynamic context associated with the generation and emplacement of this post-collisional magmatism is still enigmatic. In this study, we report new UPb ages, elemental geochemistry, mineral chemistry and SrNd isotope data for rocks from the Pajeú batholith. LA-ICP-MS zircon UPb dating revealed that this batholith was formed by at least two distinct magma pulses. The oldest pulse (ca. 592 Ma) consists mainly of porphyritic quartz monzonites to monzogranites with abundant mafic microgranular enclaves (MMEs), while the younger pulse (ca. 568 Ma) is composed of equigranular biotite granites. The porphyritic monzogranites are magnesian, have intermediate to acidic compositions (SiO2 = 62.2–67.6 wt%) and high Mg# (44–55) values. In contrast, biotite granites are ferroan, have high SiO2 (69.3–73.1 wt%) and low Mg# (16–36) values. Both rock types are characterized by enrichment in LREE and LILE and depletion in HREE and HFSE, but with more fractionated REE patterns for biotite granites ([La/Yb]N = 67.4–101.5) than for porphyritic rocks ([La/Yb]N = 35.8–54.8). The SrNd isotopic values for the different rock types are roughly similar. However, biotite granites show slightly higher initial 87Sr/86Sr (0.71265–0.71412) ratios and more negative εNd (t) (−18.45 to −18.67) values than porphyritic monzogranites (initial 87Sr/86Sr ratios from 0.71077 to 0.71155 and εNd (t) from −16.04 to −16.96). These geochemical and isotopic signatures, together with mineral chemistry data, suggest different sources for the two rock types. The biotite granites are of purely crustal origin, derived by partial melting of a Paleoproterozoic amphibolitic lower continental crust, while a mixture of melts derived from the Paleoproterozoic continental crust and magmas derived from an enriched lithospheric mantle could explain the origin of porphyritic monzogranites. Based on the spatial and temporal distribution of magmatic rocks from the Alto Pajeú Domain, we suggest that a local lithospheric thinning model could explain the evolution of post-collisional magmatism in this region of the Borborema Province.

Nd isotope systematics of Late Paleozoic granitoids from the Western Transbaikalia (Russia): Petrological consequences and plume model testing

Late Paleozoic granites of the Angara-Vitim batholith (AVB) occupy an area of 200,000 km2 in Western Transbaikalia (the eastern part of the Central Asian fold belt). Batholith granitoids form a sheet-like body with an average thickness of 7–10 km and a volume of about 1 million km3. The granitoid massifs that make up the batholith are composed of high-potassium calc-alkaline and subalkaline quartz monzonites, quartz syenites, amphibole-biotite granodiorites, and biotite granites of autochthonous and allochthonous facies. An extremely high heterogeneity of the batholith isotopic structure was established, which basically corresponds to the parameters of uneven-aged crustal metaterrigenous protoliths. There are significant variations in εNd(Т) and accordingly T(DM-2) in granitoids of different complexes. It is assumed that the isotopic heterogeneity of AVB was formed due to the melting of a limited protoliths number that are maximally contrasting in isotopic and lithological composition: the Paleoproterozoic continental crust with εNd(Т) ≈ -20 ÷ -22 and T(DM-2) = 2.9–2.5 Ga and Neoproterozoic mafic granulites of increased potassium alkalinity, enriched in the juvenile component (εNd(Т) ≈ -3.0; T(DM-2) = 1.2–1.3 Ga). The latter were the main magmas source of postbatholitic alkali granites. Melts from these contrasting protoliths were only in some cases complementary to the salic melts sources. The main mechanism that determined the isotopic composition of AVB granitoids was the mixing of isotopically contrasting magmas in different proportions. Mingling dikes, mafic inclusions in granitoids, and synplutonic mafic intrusions in the AVB indicate an additional mixing component. It was mafic magma from an enriched mantle reactivated in the Late Paleozoic under the mantle plume influence on the heated plastic crust of a young (Hercynian) orogen.

Constraints on the source and petrogenesis of early Ediacaran shoshonitic mafic magmatism and high-K calc-alkaline granitoids in the Sergipano Orogenic System, Borborema Province, Brazil

The early Ediacaran Capela pluton (ca. 630 Ma) is intruded into the metasedimentary succession of the Sergipano Orogenic System along the oriental segment of the Macururé Domain, southeastern Borborema Province, NE Brazil. This body is an uncommon example of mantle-derived shoshonitic mafic rocks associated with high-K calc-alkaline granitoids emplaced in a pre- to early-collisional context. Here, we aim to unravel the petrogenesis of this plutonic association to determine the role of crustal contribution to magmatism and its geodynamical significance during the early stages of the Brasiliano/Pan-African Orogeny. The Capela pluton comprises cumulate hornblendites, gabbronorites, gabbros, diorites, granodiorites, quartz monzonites, and granites. Shoshonitic mafic rocks and high-K calc-alkaline granitoids show significant enrichments in LILE and LREE compared to HREE and HFSE. Ultramafic and mafic rocks display a conspicuous crustal signature, yielding subchondritic εNd(t) and zircon εHf(t) values, along with variable radiogenic Sr–Pb isotopic compositions. The dominant factors controlling the geochemical features of the mafic magmas were the enriched signature of the lithospheric mantle source and the degree of partial melting. Mantle source metasomatism is thought to have occurred by incorporating subducted sediments into the mantle wedge before the onset of the Brasiliano Orogeny. Geochemical modeling demonstrated that low partial melting degrees (5–10%) of phlogopite-bearing lithospheric mantle in the spinel stability field metasomatized by 5–10% subducted sediments may account for the main characteristics of the mafic rocks. Introducing sedimentary material into the mantle caused a decrease in Sm/Nd and Lu/Hf ratios while increasing the Rb/Sr, U/Pb, and Th/Pb ratios, which led to the time-integrated evolved isotopic signature observed in the mafic rocks. The coeval granitoids are metaluminous to slightly peraluminous and display Nd–Pb isotopic compositions similar to those of mafic–ultramafic rocks. The petrological and isotopic features of the granitoids are consistent with derivation from an ancient mafic lower crustal source. We argue that the ascent and emplacement of hydrous mantle-derived magmas as successive sills into the lower crust produced a deep hot zone beneath the Sergipano Orogenic System during the onset of the Brasiliano/Pan-African Orogeny. Aqueous fluids released from such potassic mafic magmas favored the partial melting of surrounding rocks, producing contemporary felsic magmatism.

Material composition of the Mesozoic igneous rocks of the Mikhailovsky massif and small bodies of the Evotinskiy ore district (Southern Yakutia, Aldan-Stanovoi shield)

The petrographic and geochemical characteristics of the Mesozoic igneous rocks of the Mikhailovsky massif, including the sills and dikes of the Evotinsky ore district located in the central part of the Nimnyr terrane of the Aldan-Stanovoy shield, were examined. This study revealed for the first time that the Mikhailovsky Massif is composed of quartz monzonites, while the sills and dikes are composed of quartz syenites. These rocks are geochemically close to the shoshonite-latite series of island arc rocks and are enriched in LREE and depleted in HREE, characterized by aweak negative Eu-anomaly. The sequence of magmatism development in the Mesozoic has been established: the formation of rocks of the Mikhailovsky massif and most small bodies occurred in the post-collision period, followed by the intrusion of quartzsyenite dike bodies in theanorogenicstages of territorial development.The study suggeststhat all the studied igneous rocks of the northeastern part of the Evotinsky region are characterized by a duality of geochemical composition,which indicates either intense mantle-crustal interactionor the existence of two sources of both mantle and crustal originat that time.

Rejuvenation of magma reservoir: A case study of the Matou quartz monzonite in western Zhejiang

Rejuvenation of magma reservoir: A case study of the Matou quartz monzonite in western Zhejiang

MULTIPULSED MAGMATISM AND DURATION OF THE HYDROTHERMAL SYSTEM OF THE GIANT JIAMA PORPHYRY Cu SYSTEM, TIBET, CHINA

Abstract Jiama is the largest porphyry-skarn ore system in the Gangdese metallogenic belt, Tibet. It is composed of porphyry Cu-Mo, Cu-polymetallic skarn, Cu-Pb-Zn manto, and distal vein Au orebodies with associated Ag, W, and Bi. However, the precise timing of the magmatism and hydrothermal events at Jiama remains obscure. Here, using high-precision chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon dating of ore-bearing and post-ore intrusions, we accurately constrain the lifespan of magmatism and hydrothermal mineralization. Monzogranite porphyry dikes are cut by Cu-Mo vein mineralization in the deeper part of the system, indicating that they were emplaced pre-ore, and yield a crystallization age of 15.534 ± 0.007 Ma (mean square of weighted deviates [MSWD] = 0.99, n = 6). A granodiorite porphyry that cuts the monzogranite porphyry and hosts vein and disseminated chalcopyrite and molybdenite is considered synchronous with ore and yields a crystallization age of 15.368 ± 0.007 Ma (MSWD = 1.01, n = 5). These two phases of intrusions are cut by quartz-diorite porphyry bodies, which yield a crystallization age of 15.076 ± 0.006 Ma (MSWD = 0.13, n = 6) and contain weak, subeconomic Cu and almost no molybdenum mineralization. A post-ore barren quartz monzonite porphyry yields a crystallization age of 14.925 ± 0.006 Ma (MSWD = 1.12, n = 6). The lifespan of magmatism at Jiama is thus about 0.61 m.y. The difference with previous molybdenite Re-Os isochron ages from the porphyry (14.7 ± 0.3 Ma), hornfel (14.7 ± 0.4 Ma), and skarn (15.4 ± 0.2 Ma) suggests that high-precision chronology is required to decipher accurate timing of mineralization in porphyry systems such as Jiama. The 40Ar/39Ar ages of hydrothermal biotite coexisting with molybdenite in monzogranite porphyry and hornfels are 15.25 ± 0.17 Ma (MSWD = 1.6) and 15.25 ± 0.24 Ma (MSWD = 0.14), respectively, slightly younger than the granodiorite porphyry and older than weakly mineralized quartz diorite porphyry, which represents the time of the ore-forming hydrothermal event. Thus, Jiama is the product of pulsed magmatism during which a short-lived hydrothermal event formed the giant Cu polymetallic system.

Petrogenesis and Tectonic Implications of the Qulihai Pluton in the Northern Margin of the Yili Block, NW China

Abstract Despite extensive research work that has been done, whether the northern margin of the Yili Block (YB) is still an active continental margin during the early Carboniferous period is still in debate. Herein, we conducted zircon U–Pb geochronology, geochemistry, and zircon Lu–Hf isotope studies on the Qulihai pluton in the northern margin of the YB to constrain the petrogenesis and dynamic process. The Qulihai pluton is a granitoid complex that is composed of quartz diorite, quartz monzonite, and syenogranite. The zircon U–Pb dating results revealed that the pluton was formed and emplaced between 346 and 342 Ma. The three different Qulihai pluton rock types had comparable εHf(t) values, ranging from +3 to +8. The corresponding two-stage model ages of 817–1182 Ma indicated their potential derivation from the Meso-Neoproterozoic juvenile crust. The Qulihai pluton typically features medium-to-high SiO2, K2O, and Al2O3 contents and low MgO and Fe2O3T contents. The quartz diorite and quartz monzonite samples had Mg# values of 43–47, indicating the input of mantle-derived melts in the source area. In contrast, the source region of syenogranite was purely crustal material. The Qulihai pluton is mainly characterized as strong metaluminous moderate-to-high-K cal-alkaline rocks of the I-type granite series, which are enriched in large-ion lithophile elements and depleted in high field strength elements while exhibiting active continental margin island arc magmatism. Our findings, combined with the comprehensive analysis of previous studies, suggest that the Qulihai pluton formation resulted from the subduction of the North Tianshan oceanic crust beneath the YB during the early Carboniferous period, contemporary with the tectonic regime transition from subduction advance to subduction retreat.

Ordovician−Early Devonian granitic magmatism as the consequence of intracontinental orogenic activity along the Qinhang belt in South China

The early Paleozoic tectono-magmatic activity within the South China block, which is well illustrated by Ordovician−Devonian granites in the western Qinhang belt, was the response to closure of the Proto-Tethys Ocean and convergence of continental blocks. The spatiotemporal distribution and source characteristics of the granites provide us the opportunity to understand the processes and driving mechanisms of intracontinental orogeny. As an example, the Miaoershan-Yuechengling granite batholith in northern Guangxi, located along the western margin of the Qinhang orogenic belt, is mainly composed of quartz monzonite and monzogranite. All the granitic rocks from Miaoershan-Yuechengling batholith are composed of K-feldspar, quartz, plagioclase, biotite, and hornblende. Geochronologic dating indicates that the Miaoershan-Yuechengling batholith was emplaced during the late Silurian and Early Devonian, respectively. The rocks have high SiO2, with an average value of 73.29 wt%, and total alkalis (Na2O + K2O = 7.21−10.03 wt%), but low Al2O3 (12.96−15.51 wt%), showing characteristics of the high-potassium calc-alkaline series of S-type peraluminous granites (Al2O3/[CaO + Na2O + K2O] = 1.03−1.22). Trace elements in the Miaoershan-Yuechengling granitic rocks are characterized by enrichment of large ion lithophile elements and depletion of high field strength elements. Their rare earth element (REE) trends are characterized by relatively flat distribution patterns with weak light REE enrichment, weak heavy REE fractionation, and negative Eu anomalies. Zircons from the rocks have negative εHf(t) values ranging from −13.24 to −5.1, with crustal model ages (THf2) of 2.2−1.7 Ga. These features indicate that they are S-type granites with parental magmas originating from partial melting of sandy argillaceous sources of Paleoproterozoic lower continental crust. The thermal budget for Ordovician to Early Devonian magmatism is attributed either to crustal thickening in relation to intracontinental orogenic compression or to crustal thinning due to postorogenic tectonic extension during assembly and breakup of Greater Gondwana. This study reveals that the change in mantle convection systems during plate interactions acted as a major driving force for the early orogenic processes, late collapse of the orogenic belt, and massive syncollisional to postorogenic magmatism.

Magmatic‐hydrothermal evolution and mineralization mechanisms of the Wangjiazhuang Cu (‐Mo) Deposit in Zouping Volcanic Basin, Shandong Province, China: Constraints from Fluid Inclusions

AbstractWangjiazhuang Cu (‐Mo) deposit, located within the Zouping volcanic basin in western Shandong Province, China is the only one with economic value found in the area so far. In order to expound the metallogenetic characteristics of this porphyry‐like hydrothermal deposit a detailed fluid inclusion study has been conducted employing the techniques of representative sampling, fluid inclusion petrography, microthermometry, Raman spectroscopy, La‐ICP‐Ms analysis of single fluid inclusions, as well as cathode fluorescence spectrometer analysis of host mineral quartz. The deposit contains mainly two types of orebodies, i.e. veinlet‐dissemination‐stockwork orebodies in the K‐Si alteration zone and pegmatitic‐quartz sulfide veins above them. In addition, minor breccia ore occurs locally. Four types of fluid inclusions in the deposit and altered quartz monzonite are identified: L‐type one‐ or two‐phase aqueous inclusions, V‐type vapor‐rich inclusions with V/L ratios greater than 50‐90%, D‐type multiphase fluid inclusions containing daughter minerals or solids and S‐type silicate‐bearing fluid inclusions containing mainly muscovite and biotite. Ore petrography and fluid inclusion study has revealed a three‐stage mineralization process driven by magmatic‐hydrothermal fluid activity as follows. Initially a hydrothermal fluid separated from the parent magma infiltrated into the quartz monzonite, resulting in its extensive K‐Si alteration as indicated by silicate‐bearing fluid inclusions trapped in altered quartz monzonite. This is followed by the early mineralization, the formation of quartz veinlets and dissemination‐stockwork ores. During the main mineralization stage due to the participation and mixing of meteoric groundwater with the magmatic‐sourced hydrothermal fluid the cooling and phase separation caused deposition of metals from the hydrothermal fluids. As a result the pegmatitic‐quartz sulfide‐vein ores formed. In the late mineralization stage, decreasing in fluid salinity has led to the formation of L‐type aqueous inclusions and chalcopyrite‐sulfosalt ore. Coexistence of V‐type and D‐type inclusions and their similar homogenization temperatures but different homogenization modes suggest that phase separation or boiling of the ore‐forming fluids once took place during the early and the main mineralization stages. The formation P‐T conditions of S‐type inclusions, and the early and the main mineralization stages are estimated as ca. 156 ∼ 182 MPa and 450 ∼ 650 °C, 350‐450 °C, 18‐35 MPa and 280‐380 °C, 8‐15 MPa, respectively based on the microthermometric data of the fluid inclusions formed at the individual stages.

Petrogenesis of the early Permian Hongliujing granite complex in the Chinese Eastern Tianshan orogen: Evidence for crustal growth in the Central Tianshan microcontinent

The generation and modification of silicic magma systems are essential processes in resolving the differentiation of continental crust. This understanding motivated the geochronological and geochemical study of the early Permian Hongliujing granite complex, consisting of quartz monzonite, granite, and leucogranite in the Central Tianshan microcontinent of the southern Central Asian Orogenic Belt. Laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) zircon U-Pb dating of the Hongliujing complex rock units revealed almost identical ages (279 ± 2 Ma to 270 ± 2 Ma). The high-silica leucogranite and granite are characterized by positive Rb and negative Eu anomalies and Ba, Sr, P, and Ti depletions. The zircon trace elements are characterized by relatively low Ti and Th/U and high Yb/Gd. In contrast, the quartz monzonite and its mafic microgranular enclaves display minor negative Ba, Sr, P, Ti, and Eu anomalies, while the zircon trace elements are characterized by relatively high Ti and Th/U and low Yb/Gd. The complex has similar zircon Hf and whole-rock Nd isotopic compositions, with Hf and Nd model ages younger than 1.4 Ga, suggesting that their magmas were derived from an isotopically depleted mantle, with some contributions from crustal melts. The leucogranites further showed relatively large variations of εHf(t) and lower εNd(t) values, implying that their magma was affected by higher amounts of crustal contamination. We suggest that crystal-melt segregation was the major mechanism responsible for the evolution of the magmatic system, and that the early Permian magmatism represents a crust-forming episode triggered by slab rollback of the subducting South Tianshan oceanic plate beneath the eastern Central Tianshan microcontinent. Thus, our study reveals that microcontinents with Precambrian crustal basement were major sites of juvenile continental growth during the accretionary evolution of the Central Asian Orogenic Belt.

Petrogenesis, geochronology and thermochronology of Oligocene to Miocene Western Anatolia granitoid plutons in Turkey

Western Anatolia (WA) hosts numerous I-and S-type plutons with variable compositions. This paper presents new comprehensive geology, petrography, bulk-rock and mineral chemistry, SrNd isotope, zircon UPb, biotite and hornblende Ar/Ar and first apatite UTh / He age data for seven plutons (Baklan, Evciler, Eybek, Ilıca-Şamlı, Kozak, Uludağ, Yenice) in WA. Western Anatolia granitoid plutons (WAGPs) are mainly granodiorite, with minor monzonite, diorite, quartz monzonite and granite. The dominant minerals are K-feldspar (usually orthoclase and rarely microcline), plagioclase (albite, oligoclase), amphibole (hornblende), biotite, quartz, and accessory minerals are titanite, zircon, apatite, and opaques. The crystallization temperatures are relatively uniform (640-740 °C) but pressures range from those typical of the upper crust to those typical of the mid crust. The plutons are characterized by moderate to high SiO2 (58.1–73.7 wt%), K2O (2.1–6.9 wt%), and relatively low P2O5 (0.03–0.60 wt%) and most are I-type and metaluminous, except for the Uludağ pluton that is S-type. They are enriched in large ion lithophile elements (LILEs e.g. U, Th, Rb, and K), light rare earth elements (LREEs) and Pb, and depleted in heavy rare earth elements (HREEs), high field strength elements (HFSE, e.g. Nb, Ti) and Sr, Ba and P relative to other LILEs. The plutons display small Eu anomalies (Eu/Eu*: 0.17–1.15) due to probaly suppression of feldspar fractionation/or partial melting of lower crust. They have relatively high initial 87Sr/86Sr = 0.705775–0.708357 and low initial 143Nd/144Nd = 0.512290–0.512581. The LA-ICP-MS 206Pb238U age analyses of zircon in addition to 40Ar/39Ar dating of hornblendes and biotites suggest that the plutons were emplaced between 29.4 Ma and 19.8 Ma and cooled with a relatively high rate (∼363 °C/Ma). These ages correlate with the collision between the Sakarya Zone and Anatolide–Tauride Platform in Rupelian to Burdigalian time. The (UTh)/He apatite ages range from 19.8 Ma to 7.6 Ma, for the WA granitoid plutons and indicates that the crustal terrains hosting the seven plutons had complex exhumation histories within their arc environment. Consequently, these ages constrain the crystallization, cooling and exumation times of the Oligocene to Miocene plutons in a post-collisional setting on the northern margin of Gondwana.

Petrogenesis of Jurassic granitic plutons in the Yanbian area, NE China: Implications for the subduction history of the Paleo-Pacific Plate

It is widely accepted that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent began during the early Mesozoic; however, the details of the subduction process remain uncertain. This paper presents new zircon U–Pb–Hf and whole-rock geochemical data for Jurassic intrusive rocks from the Yanbian area of NE China to provide a better understanding of the subduction history of the Paleo-Pacific Plate. Zircon U–Pb dating results reveal that three stages of Jurassic magmatism are recorded in the Yanbian area, namely, Early Jurassic (188–179 Ma), Middle Jurassic (172–163 Ma), and Late Jurassic (158–156 Ma). Early Jurassic intrusive rocks from the Yanbian area are predominantly calc-alkaline gabbro, gabbro-diorite, quartz monzonite, granodiorite, and syenogranite. These geochemical features and rock associations are indicative of formation in an active continental margin setting related to the initial subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The Early Jurassic granitoids were formed mainly by the partial melting of heterogeneous lower crust. The Middle Jurassic granitoids are geochemically similar to adakites and have εHf(t) values of + 2.0 to + 10.1. These rocks are inferred to have been derived from magmas generated by the partial melting of thickened juvenile lower-crustal material. Their formation was related to the subduction of the Paleo-Pacific Plate. Late Jurassic adakites in the Yanbian area formed in a compressional tectonic setting. Their negative εHf(t) values (−17.2 to − 8.6) and TDM2 ages (2025–1552 Ma) indicate that the primary magma was derived from the partial melting of ancient continental crust. Combining our data with the distribution of Late Jurassic igneous rocks in the NE Asian continental margin and the northward migration of Jurassic accretionary complexes along the margin, we conclude that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent during the Late Jurassic–earliest Early Cretaceous had a low angle of obliquity.

The geochronology, geochemistry, and petrogenesis of the Leimengou porphyries, Qinling Orogen: A case study of intrusions associated with a Dabie-type porphyry Mo deposit

The Leimengou giant Mo deposit is a porphyry system in the northeastern Qinling Orogen along the southern margin of the North China Craton, comprising orebodies hosted mainly in a multiphase porphyritic granitic to monzonitic pluton emplaced in the Taihua Supergroup. Zircons from the syn-ore porphyritic monzogranite (PMG) and the porphyritic K-feldspar granite (PKG) yielded U − Pb ages of 131.3 ± 1.0 Ma and 130.6 ± 0.9 Ma, respectively. The post-ore, quartz monzonite porphyry (QMP), has a weighted mean 206Pb/238U age of 124.6 ± 1.0 Ma (n = 14, 1σ, MSWD = 0.13). These ages constrain the Leimengou porphyry system to have formed between 132 and 124 Ma. The PMG and PKG have similar geochemical characteristics, i.e., high-K calc-alkaline affinity, negative εHf(t) values of − 25.1 to − 22.0 and − 25.1 to − 19.2, and TDM2 ages of 2.77–2.57 Ga and 2.76–2.40 Ga, respectively. The PKG has lower concentrations for Sr, Ba, and negative anomalies of δEu, and also has higher total REE values compared to the PMG. These anomalies are interpreted to reflect fractional crystallization involving plagioclase and biotite. The characteristics of the PKG support its derivation from an evolved magma, which likely facilitated the enrichment of Mo. Additionally, the Hf isotope data suggest that the Leimengou porphyry system had a composite source, with inputs from the North Qinling Accretion Belt, the North China Craton, and the mantle. Compared to the syn-ore PMG, the post-ore QMP exhibits lower (La/Yb)N ratios of 20.5–22.8, higher zircon εHf(t) values of − 19.7 to − 9.0, and younger TDM2 ages of 2.42–1.75 Ga. This suggests that the Leimengou porphyry Mo system formed during thinning of an overthickened orogenic crust during the tectonic transition from collisional compression to post-collisional extension. The productive intrusions at Leimengou and other porphyry Mo deposits of Dabie-type have average Nb/Zr ratios that are typically below 1. Moreover, the Rb/Sr ratios range from 0.1 to 1, further distinguishing these intrusions from the intrusions associated with Climax- and Endako-type Mo deposits.

Petrogenesis of Neoproterozoic high-K intrusion in the southwestern Yangtze Block, South China: Implication for the recycled subducted-sediment in the mantle source

The study of K-enriched intrusive rocks is essential for deciphering mantle metasomatism beneath active continental arcs. In this contribution, high-precision zircon U–Pb–Hf isotope, whole-rock geochemistry, Sr–Nd isotope, and mineral chemistry analyses were performed to evaluate the petrogenesis and geodynamic system of the Yunnongfeng intrusion on the southwestern margin of the Yangtze Block. The Yunnongfeng intrusion consists of a high-K to shoshonitic rock assemblage with variable lithology from gabbro-diorite to granite. Zircon U–Pb dating gives concordant crystallization ages of ca. 782.5 ± 3.8 Ma for gabbro-diorite, ca. 774 ± 4.1 and 776 ± 4.1 Ma for diorite, ca. 770 ± 4.7 Ma for quartz monzonite, ca. 763 ± 3.4 Ma for quartz syenite, and ca. 764 ± 16 Ma for granite. These samples also show similar Sr–Nd, and Lu–Hf isotopic compositions, implying a common magma source. The similar crystallization age and regular variation of major and trace element contents suggest that these rocks were formed through fractional crystallization of cogenetic primitive mantle magmas. The enriched εNd(t) (−5.7 to − 5.1) and εHf(t) (−6.7 to − 1.2) values, high Rb/Y and Th/La ratios, slight Nd–Hf decoupling, and high-K and Th contents demonstrate that their lithospheric mantle source was enriched by slab-related fluid and sediment-related melt. The samples also exhibit remarkable enrichment in large-ion lithophile elements and depletion in high-field-strength elements, indicative of subduction-related arc magmatism. Taking into account previous studies, we suggest that the western margin of the Yangtze Block experienced a long-term subduction process during the Neoproterozoic, and the Yunnongfeng intrusion formed in an extensional back-arc basin. Based on the K-enriched mafic–intermediate rocks from the western margin of the Yangtze Block commonly show high K2O/Na2O, Rb/Sr, low Ba/Rb ratios, and enriched εNd(t) values, our study, coupled with numerous previous reports, proposes that the K-enrichment resulted from the breakdown of phlogopite, owing to subduction-related sediment melt reacting with peridotite in the mantle source area.

Petrogenesis and implications for tin mineralization of the Beidashan granitic pluton, southern Great Xing'an Range, NE China: Constraints from whole-rock and accessory mineral geochemistry

The Beidashan pluton, consisting of quartz monzonite in the northeast and biotite granite in the southwest, is a representative granitic intrusion in the southern Great Xing'an Range. To investigate its petrogenesis and relationship with tin mineralization, whole-rock and accessory minerals (zircon and apatite) geochemical analyses were carried out. The quartz monzonite mainly belongs to high-K calc-alkaline strongly peraluminous granite, and the biotite granite is high-K calc-alkaline weakly peraluminous granite. Zircon U-Pb dating indicates a younger age for the biotite granite (138 Ma) than the quartz monzonite (140 Ma). The zircon Hf and apatite Nd isotopic compositions of the quartz monzonite (εHf(t) = 5.2 to 9.1 and εNd(t) = −1.1 to 1.3) and those of the biotite granite (εHf(t) = 5.6 to 8.0 and εNd(t) = −0.9 to 1.0) are indistinguishable, implying that they were derived from the same sources. Modeling results using apatite Nd isotope data show that they were from a mixing source of the Xilinhot Group and mantle-derived basaltic melt. Whole-rock and apatite trace elements reveal that the granitic magma mainly experienced fractional crystallization of amphibole, biotite, plagioclase, K-feldspar, apatite, and monazite from the quartz monzonite to the biotite granite. Mineralogical, whole-rock geochemical, and apatite trace element data indicate that the Beidashan pluton has an I-type granite affinity. A crystal mush model was proposed accounting for the composition gap between these two granites (e.g., SiO2, Al2O3, and Ba), in which the biotite granite represents the highly fractionated interstitial melt extracted from the crystal mush system whereas the quartz monzonite is the residual crystal mush consisting of the cumulate crystals and trapped interstitial melt. The melt was extracted when the crystallinity of the crystal mush reached about 33–37%, and the residual crystal mush trapped about 38–46% interstitial melt. Both Ce anomalies in zircon and Eu anomalies in apatite imply reducing conditions. The calculated values of oxygen fugacity for the Beidashan pluton range from −19.3 to −15.7, and most of them are lower than the fayalite-magnetite-quartz (FMQ) oxygen buffer. Apatite in the Beidashan pluton has high F (2.35–3.61%) and low Cl (0–0.41%) concentrations, which are similar to those of Sn-W deposits worldwide. The Sn contents of apatite increase from the quartz monzonite (mean 0.30 ppm) to the biotite granite (mean 1.09 ppm), suggesting that magma evolution is important for the enrichment of Sn in the melt.

Genesis and Evolution of the Yolindi Cu-Fe Skarn Deposit in the Biga Peninsula (NW Turkey): Insights from Genetic Relationships with Calc-Alkaline Magmatic Activity

The current work investigates the impact of magmatic fluids and metasomatic processes on the Yolindi Cu-Fe skarn deposit in the Biga Peninsula, Turkey. It traces the stages of skarn evolution, from prograde to retrograde alterations, and investigates findings within a broader geological, mineralogical, and geochemical framework. Additionally, it assesses the evolutionary history of the Yolindi deposit in relation to calc-alkaline magmatic activity in an island-arc environment and compares its mineral compositions and genesis with other global and regional Cu-Fe skarn deposits. The Yolindi Cu-Fe skarn deposit in the Biga Peninsula was formed by the intrusion of Şaroluk quartz monzonite pluton into Upper Paleozoic Torasan Formation rocks such as phyllite, schists, hornfels, marble, and serpentinites. During skarnification, reactions between the magmatic fluids from the Şaroluk quartz monzonite pluton and the Torasan Formation produced skarn minerals associated with metals such as Fe and Cu. Initially, these reactions formed prograde skarn minerals such as augite-rich pyroxenes and andradite garnets with magnetite and pyrite. As the system cooled, these initial minerals underwent retrograde alteration, leading to the formation of minerals such as epidote, actinolite, and chlorite, as well as other copper and iron minerals including chalcopyrite, bornite, secondary magnetite, and specular hematite. Therefore, four main stages influenced the formation of the Yolindi Cu-Fe deposit: metamorphic bimetasomatic, prograde metasomatic, and retrograde metasomatic stages. Later, oxidation and weathering resulted in supergene minerals such as cerussite, malachite, and goethite, which serve as examples of the post-metamorphic stage. The mineralogical shifts, such as the andradite–grossular transition, reflect changing hydrothermal fluid compositions and characteristics due to the addition of meteoric fluids. Importantly, the formation of magnetite after garnet and clinopyroxene during the retrograde stage is evidenced by magnetite crystals within garnet. The mineral associations of the Yolindi Cu-Fe skarn deposit align with the global skarn deposits and specific Turkish skarns (e.g., Ayazmant Fe-Cu and Evciler Cu-Au skarn deposits). The Yolindi Cu-Fe skarn deposit, in association with ore-bearing solutions having magmatic origins, developed in an island-arc setting.

Building and reworking of Archean continental crust in the nucleus of the Yangtze Craton: Constraint from 3.4 Ga and 2.94 Ga granitoid gneisses in the Southern Kongling Complex

The TTG gneisses, a dominant lithological assemblage within Archean cratonic provinces, provide a window into the early evolution of the continental crust. The Kongling complex in South China preserves voluminous Archean granitoids, recording the early formation and evolution history of the Yangtze Craton. We present results of a comprehensive study involving field investigation, petrographic characterization, zircon U–Pb geochronology and Lu-Hf isotope tracing, and whole-rock geochemistry for the Archean granitoid gneisses from the Southern Kongling Complex. Igneous zircons from two granitic gneisses yielded weighted mean 207Pb/206Pb ages of 3399 ± 15 Ma (MSWD = 0.99, n = 24) and 3389 ± 12 Ma (MSWD = 1.02, n = 20). Zircons from the 3.4 Ga granitic gneiss also record a ca.3.0 Ga anatexis event which is contemporaneous with the widespread granitoid gneisses in the Kongling Complex. Geochemical and zircon Hf isotope data (εHf(t) values of − 3.41 to + 0.77 and two-stage Hf model ages of 3.65–3.80 Ga) for the granitic gneisses support a derivation from pre-existing Eoarchean (TDM2 = 3.73 Ga) crust. LA-ICP-MS zircon U-Pb dating yielded emplacement ages of 2948 ± 17 Ma for a migmatized trondhjemitic gneiss, and 2928 ± 14 Ma for a quartz monzonite gneiss. These two gneisses have similar zircon Hf model ages (TDM2 = 3.45 Ga) and both were emplaced during a major phase of mafic magma diapiric process that significantly reworked the old crust. The occurrences of 2.94 Ga trondhjemite and associated mafic blocks suggest intra-crustal differentiation by partial melting of low-K mafic rocks. We suggest that intra-crustal remelting and differentiation played a key role in the formation, evolution, and maturation of the micro-continents in Kongling during the Paleo- to Meso-Archean. The whole-rock geochemical and zircon Hf isotopic compositions of the different generations of granitoid gneisses from the Southern Kongling Complex are similar to those of the coeval gneisses (3.45 Ga and 2.95 Ga) from the northern part of the Kongling Complex, indicating a common tectono-magmatic history shared by both segments tracing back to as early as 3.4 Ga. The Archean granitoid gneisses from the Kongling Complex record remelting and differentiation of Eo- to Paleo-Archean crusts during the Paleo- to Meso-Archean, implying that Eoarchean crust is likely to have been preserved within the Kongling complex.