New evidence on the timing of southern Neotethys closure from geochronology and geochemistry of Harmanlı region ophiolite (southeastern Anatolia) and Late Cretaceous granitic rocks

سنگ شناسی، سن سنجی، ژئوشیمی و تعیین منشأ توده های گرانیتوئیدی منطقه بجستان، شمال فردوس، استان خراسان رضوی

Oligocene subduction-related plutonism in the Nodoushan area, Urumieh-Dokhtar magmatic belt: Petrogenetic constraints from U–Pb zircon geochronology and isotope geochemistry

The Zhashui-Shanyang ore cluster area is one of the most important gold polymetallic ones in northwestern China. The Qinglingou gold deposit is a newly discovered small-scale deposit in the Zhashui-Shanyang area. Gold mineralization closely related to acid intrusive rocks has been found for the first time in this area. In this paper, the geochronology, whole-rock geochemistry, and isotope signature of the granite porphyries in the deposit are studied. They are characterized by variable medium SiO2 (67.22–71.72 wt.%), high K2O + Na2O contents (6.54–10.34 wt.%), and variable Al2O3 (14.47–15.10 wt.%) values. The A/CNK ratios range from 0.90 to 1.23, and the A/NK ratios vary from 1.14 to 1.48. These rocks also contain biotite and amphiboles and are similar to peraluminous and high-K calc-alkaline I-type granites. The Qinglingou granite porphyries show relative enrichment of Rb, Th, and K, and depletion of Nb, Ta, P, Ti, and other high field strength elements. These porphyries are enriched in light rare earth elements relative to heavy rare earth elements with weak negative Eu anomalies (δEu = 0.63–0.89), which is interpreted to be the best age of crystallization of the Qinglingou porphyries. LA–ICPMS zircon U–Pb dating yields an age of 211 ± 1.2 Ma (n = 16, MSWD = 0.39). The close spatial relationship between the ore bodies and granite porphyry dikes indicates that this age may represent the metallogenic age in this area. The zircons have 176Hf/177Hf ratios ranging from 0.282625 to 0.282702, the εHf(t) values are near 0 and the two-stage zircon Hf model ages range from 1121 to 1296 Ma. These data indicate that the Qinglingou granite porphyries were derived from the interplay between mantle- and crustal-derived magmas. We therefore propose that there is potential gold in carbonate rocks at the periphery of porphyry-skarn copper-molybdenum deposits.

U–Pb zircon geochronology and geochemistry of Neoproterozoic volcanic rocks in the Tarim Block of northwest China: implications for the breakup of Rodinia supercontinent and Neoproterozoic glaciations

Zircon U[sbnd]Pb geochronology and isotopic geochemistry of the Tangjiaping Mo deposit, Dabie Shan, eastern China: Implications for ore genesis and tectonic setting

Abundant Early Cretaceous magmatism is conserved in the central and southern Great Xing’an Range (GXR) and has significant geodynamic implications for the study of the Late Mesozoic tectonic framework of northeast China. In this study, we provide new high-precision U–Pb zircon geochronology, whole-rock geochemistry, and zircon Hf isotopic data for representative intrusive rocks from the northern part of the Ulanhot area to illustrate the petrogenesis types and magma source of these rocks and evaluate the tectonic setting of the central-southern GXR. Laser ablation inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon U–Pb dating showed that magmatism in the Ulanhot area (monzonite porphyry: 128.07 ± 0.62 Ma, quartz monzonite porphyry: 127.47 ± 0.36, quartz porphyry: 124.85 ± 0.34, and granite porphyry: 124.15 ± 0.31 Ma) occurred during the Early Cretaceous. Geochemically, monzonite porphyry belongs to the metaluminous and alkaline series rocks and is characterized by high Al2O3 (average 17.74 wt.%) and TiO2 (average 0.88 wt.%) and low Ni (average 4.63 ppm), Cr (average 6.69 ppm), Mg# (average 31.11), Y (average 15.16 ppm), and Yb (average 1.62 ppm) content with enrichment in Ba, K, Pb, Sr, Zr, and Hf and depletion in Ti, Nb, and Ta. The granitic rocks (e.g., quartz monzonite porphyry, quartz porphyry, and granite porphyry) pertain to the category of high-K calc-alkaline rocks and are characterized by high SiO2 content (>66 wt.%) and low MgO (average 0.69 wt.%), Mg# (average 31.49 ppm), Ni (average 2.78 ppm), and Cr (average 8.10 ppm) content, showing an affinity to I-type granite accompanied by Nb, Ta, P, and Ti depletion and negative Eu anomalies (δEu = 0.57–0.96; average 0.82). The Hf isotopic data suggest that these rocks were the product of the partial melting of juvenile crustal rocks. Notably, fractionation crystallization plays a crucial role in the process of magma emplacement. Combining our study with published ones, we proposed that the Early Cretaceous intrusive rocks in the Ulanhot area were formed in an extensional tectonic background and compactly related to the subduction of the Paleo-Pacific Ocean plate.

The Guadalcazar is located in the Mesa Central (MC) province, which is mainly composed of granitic rocks and is known for its metallogenetic. The granitic rocks contain complex Sn-Hg-Ag-F mineralization and were emplaced during Eocene to Oligocene. However, the source, origin, and evolution of magma and the tectonic setting of this magmatic area have never been explained. In this study, we have conducted petrology, whole-rock geochemistry, and U–Pb zircon geochronology on granitic rocks from the Guadalcazar to constrain the petrogenesis and tectonic environment. LA-ICP-SF-MS zircon U–Pb dating shows that the Guadalcazar granite was emplaced ca. 31 Ma. These rocks are characterized by high (SiO2) contents (64–75 wt%), low CaO (0.28–1.78 wt%), with relatively high (FeOt)adj/(FeOt + MgO) values ranging from 0.90 to 0.98. The geochemical diagrams of SiO2 vs [(FeOt)/(FeOt + MgO)] and SiO2 vs [(Na2O + K2O) − CaO] show the ferroan and mostly alkali-calcic nature of these rocks. The granite shows an A2-type affinity and is strongly peraluminous, with ASI (molar Al2O3/[CaO + Na2O + K2O]) values of 1.13 to 2.60. These granitic rocks are characterized by enrichments in rare earth elements (REE) and high field strength elements (HFSE), and depletion in Ba, Nb, Sr, Ti, and Eu. These features suggest that these A-type granites were derived from the metasedimentary rocks and evolved through extensive fractional crystallization. The multidimensional discrimination diagrams showed a continental rift or within-plate setting. By combining previous and new data, we proposed a new magmatic evolution model that supports an extension during ca. 34–28 Ma in the Guadalcazar, central Mexico.

LA-ICP-MS U–Pb zircon geochronology and geochemistry of Paleoproterozoic mafic dykes from western Shandong Province: Implications for back-arc basin magmatism in the Eastern Block, North China Craton

Geochemistry, zircon U–Pb and Lu–Hf isotopes of an Early Cretaceous intrusive suite in northeastern Jiangxi Province, South China Block: Implications for petrogenesis, crust/mantle interactions and geodynamic processes

Triassic diorites and granitoids in the Foping area: Constraints on the conversion from subduction to collision in the Qinling orogen, China

Permian granitoid emplacement represents one of the most important tectonothermal events in the northern margin of the North China Craton (NCC). In this study, we collected geochronological and geochemical data of the regional Permian granitoid in the northwestern margin of the NCC, and investigated the Dongshengmiao pluton, using it as an example to constrain the regional granitoid petrogenesis and its geodynamic settings. The Dongshengmiao pluton contains porphyritic granite and quartz diorite. LA-ICP-MS zircon U-Pb dating results have constrained the granitoid emplacement to be ca. 287‒275 Ma. The Dongshengmiao granitoids have a SiO2 range of 58.4‒76.5%, moderate to high alkali content (Na2O + K2O = 5.16–7.94%), and are rich in large-ion lithophile elements (LILEs; e.g. Rb, Ba) and depleted in high-field strength elements (HFSEs; e.g. Nb, Ta, Ti). The zircons in quartz diorite have εHf(t) values of −15.6 to −11.1 with two-stage Hf model ages (TDM2) of 1997–2281 Ma, suggesting that the magma was derived from partial melting of old continental materials. In contrast, porphyritic granite shows variable Hf isotopic composition with εHf(t) values of −13.7 to −2.6 and TDM2 of 1471–2167 Ma, indicating a heterogeneous magma source. Besides the Dongshengmiao pluton, all the Permian granitoids in the northwestern margin of the NCC exhibit similar geochemical characteristics, including enrichment in LILEs, depletion in Nb and Ta, and enriched Hf isotopic signatures. The comprehensive geochemical data indicate that these Permian granitoids are derived from magma mixing between dominant partial melting of ancient felsic crustal materials and minor juvenile basaltic magma. Tectonically, the Dongshengmiao and other granitoids in the northwestern margin of the NCC may have been formed in a post-collisional extensional setting.

The Qingbulake mafic complex hosting a copper–nickel sulfide deposit, Tekesi County, West Tianshan (Xinjiang Uygur Autonomous Region) consists of pyroxene diorite–gabbro, olivine gabbro–pyroxenite, pyroxenite–olivine gabbro, and clinopyroxene peridotite. The geochemical study presented in this paper indicates that the complex is characterised by low Ti, depletion in Nb and Ta, enrichment in LILEs and slight enrichment in light REEs. These geochemical characteristics, combined with isotope systematics, suggest that the formation of the complex may be related to the subduction of the South Tianshan oceanic plate beneath the Central Tianshan plate and their collision and that the magma could be derived from a depleted MORB-source mantle. The magma underwent weak hybridisation with the crust and country rocks during its emplacement. SHRIMP U–Pb dating of zircons in pyroxene diorite samples from the Qingbulake complex yielded a concordia age of 434.4 ± 6.2 Ma, indicating that the complex was emplaced in the early Silurian (Llandovery). The features of island-arc magma shown by the Qingbulake complex were probably induced by the subduction of oceanic crust beneath the depleted mantle.

The Ankara–Erzincan suture zone includes large bodies of ophiolite and ophiolitic melange in northeastern Anatolia. The ophiolitic bodies are (1) Refahiye (Erzincan), (2) Şahvelet (Erzurum), (3) Karadağ (Erzurum) and (4) Kırdağ (Erzurum). The ophiolite-related units include well-preserved sections of oceanic lithospheric and accretionary melanges with local blueschist assemblages. The ophiolite-related units in NE Anatolia are unconformably overlain by Campanian–Maastrichtian-aged sediments that were later imbricated with the ophiolitic rocks. Geochemical data for the individual ophiolite sections indicate a tholeiitic composition, depletion in Nb, enrichment in large ion lithophile elements, parallel to slightly depleted high field strength element patterns (compared with normal-mid ocean ridge basalt), and slightly light rare earth element-depleted to parallel rare earth element trends. These features suggest progressive source depletion towards island arc tholeiites and finally boninites. A fore-arc setting is proposed for the generation of the ophiolites. In contrast, the volcanic rocks from the mélange units exhibit tholeiitic to alkaline compositions and either depletion or enrichment of rare earth element and high field strength elements. Seamount-type alkaline and subduction-related tholeiitic basaltic rocks were apparently juxtaposed during subduction/accretion. Models involving either a single north-dipping subduction zone or two north-dipping subduction zones may be applicable. Both models involve the generation of supra-subduction zone-type ophiolites in a forearc setting, an accretionary prism (with blueschists) and a volcanic arc during the Late Cretaceous. The ophiolites, ophiolitic melange and related blueschists were emplaced either northwards onto the Pontide margin or southwards over the passive margin of the Tauride platform.

曲林岩体位于冈底斯带中段的南缘，为渐新世-中新世复合岩体，主体为粗粒花岗斑岩，被后期煌斑质、花岗闪长质和花岗质岩脉切割，是多期岩浆作用的产物，出露面积约8km²。花岗斑岩两组样品（T0849-PG和T0849-G）的锆石U-Pb定年结果分别为29.7±0.1Ma和30.0±0.2Ma。花岗斑岩为高钾，准铝质，低MgO，高度富集轻稀土元素（LREE）和大离子亲石元素（LILE），亏损重稀土元素（HREE）和高场强元素（HFSE）。此外具有高Sr、Sr/Y、（La/Yb）_N；低Y和Yb，弱Eu负异常等特征。岩体内发育一系列近南北向展布的花岗闪长玢岩脉，其中两组样品的锆石U-Pb定年结果分别为15.5±0.1Ma（T0848-PY）和14.4±0.1Ma（T0850）。两条花岗闪长玢岩脉具有与岩体主体相似的稀土和微量元素分布模式，同样富集轻稀土及大离子亲石元素，亏损重稀土及高场强元素。花岗斑岩的⁸⁷Sr/⁸⁶Sr_（i）=0.706102~0.706202，ε_Nd（t）=-0.6~+0.6，锆石ε_Hf（t）=+4.9~+7.9；花岗闪长玢岩脉的⁸⁷Sr/⁸⁶Sr_（i）=0.705429~0.705474，ε_Nd（t）=-1.4~-0.2，锆石ε_Hf（t）=+2.6~+7.6。本文数据和文献数据结果表明：曲林花岗斑岩与花岗闪长玢岩脉均来源于加厚南拉萨下地壳的部分熔融，很可能与增厚的深部岩石圈的拆沉或俯冲印度岩石圈的撕裂诱发软流圈上涌有关。;The Qulin pluton is located at the southern edge of the middle part of Gangdese belt. As an Oligocene-Miocene pluton, its main body is coarse-grained granite porphyry, which was later staged by lamproitic, granodioritic, and granitic dikes which are the products of multi-stage magmatism, with an exposed area of about 8km². The zircon U-Pb dating results of two samples of granite porphyry are ~30Ma. Whole rock geochemical studies show that granite porphyry is high potassium and quasi-aluminum, characterized by low MgO together with enriched light rare earth elements (LREE) and large ion lithophile elements (LILE), depleted heavy rare earth elements (HREE) and high field strength elements (HFSE). In addition, it has the characteristics of high Sr, Sr/Y, (La/Yb)_N; low Y and Yb, and weak Eu negative anomaly. A series of nearly N-S trending granodiorite porphyrite dikes occur in the pluton, among which the zircon U-Pb dating results of two samples are 15.5±0.1Ma and 14.4±0.1Ma, respectively. They have similar distribution patterns of rare earth and trace elements as the main body of pluton. And they are also rich in LREE and LILE, along with depleting HREE and HFSE. The ⁸⁷Sr/⁸⁶Sr_(i) values of granite porphyry range from 0.706102 to 0.706202, ε_Nd(t) of which from -0.6 to +0.6, and zircon ε_Hf(t) of which from +4.9 to +7.9; while for granodiorite porphyrite dikes, the ⁸⁷Sr/⁸⁶Sr_(i) values range from 0.705429 to 0.705474, ε_Nd(t) from -1.4 to -0.2, and zircon ε_Hf(t) from +2.6 to +7.6. The new data and literature data results show that: both the granite porphyry and granodiorite porphyrite dikes of the Qulin pluton origined from the partial melting of the thickened lower crust beneath Lhasa terrane, possibly related to the upwelling of asthenosphere induced by delamination of thickened lithosphere or tearing of the Indian lithospheric slab.

Magma emplacement, differentiation and cooling in the middle crust: Integrated zircon geochronological–geochemical constraints from the Bergell Intrusion, Central Alps