Origin and tectonic implications of granitoids from the eastern segment of the South Altyn Block, North‐western China: Constraints from petrogeochemistry, zircon U–Pb dating, and Lu–Hf isotope geochemistry

Niu, Huapeng; Jiao, Xiaoqin; Xie, Qingbin; Zhang, Yongshu; Li, Xin; Wu, Zhenyu; Wang, Bo; Yang, Xin; Li, Yanan; Gao, Zijie

doi:10.1002/gj.3863

Cited by 4 publications

(2 citation statements)

References 80 publications

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“…This belt is characterized by serpentinite, mantle peridotite, gabbro, basaltic lava and diabase occurring as blocks or intrusions within the Early Palaeozoic flysch‐type sedimentary rocks (Li et al, 2009; Liu et al, 1998; Wang et al, 1999). A long time span of intermediate‐felsic magmatism (511–264 Ma) also occurred in this belt (Niu et al, 2020; Wu et al, 2018; Xu et al, 2020).…”

Section: Geological Setting and Samplingsmentioning

confidence: 96%

Middle to Late Ordovician flare‐up of granitoids, South Altyn Tagh: Reworking of exhumed continental crust

Zhou,

Zhao,

Yao

et al. 2024

Geological Journal

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A flare‐up of granitoids occurred at 465–445 Ma in the South Altyn Tagh, synchronously with the exhumation of subducted continental crust. Nevertheless, it remains enigmatic whether a petrogenetic connection exists between them. Here, we report a 454–451 Ma monzogranite pluton, which is characterized by abundant inherited zircons, located in the northern margin of the South Altyn Tagh high‐pressure (HP)—ultrahigh‐pressure (UHP) metamorphic terrane. U–Pb ages and Hf–O isotopic compositions of inherited and synmagmatic zircons are investigated to trace the source rocks and petrogenesis of this pluton. The inherited zircons (zircons that predate the magmatism) exhibit a wide range of ages from 2618 to 484 Ma, displaying three major peaks at 1800–1100 Ma, 1000–800 Ma and 500 Ma. By comparing these inheritance age patterns with zircon spectra of main (meta‐)sedimentary sequences and the widespread Early Neoproterozoic granites (presently as granitic gneisses) in South Altyn Tagh, along with zircon εHf(t) and whole‐rock Nd isotopic composition, we argue that the main source rocks of the studied monzogranite are Early Neoproterozoic granitic gneisses and Late Mesoproterozoic paragneisses from the South Altyn Tagh HP–UHP metamorphic terrane. The ca. 500 Ma inherited zircons have a metamorphic origin, which is simultaneous with the peak metamorphic ages of HP–UHP metamorphic rocks in the Altyn Tagh Complex. These observations indicate that the source rocks of the monzogranite pluton are the subducted continental crust, which underwent metamorphism at ca. 500 Ma and followed by partial melting at 454–451 Ma. In addition, synmagmatic zircons exhibit variable δ18O and εHf(t) values ranging from 5.4 to 11.7‰ and from −19 to +10.3, respectively, indicating a minor contribution of mantle‐derived melts in the formation of the monzogranite. Given the studied pluton and contemporaneous extensive granitoids (465–445 Ma), characterized by similar geochemistry and source rocks, are synchronous with the final exhumation of subducted South Altyn Tagh continental crust, we propose that the reworking of exhumed continental crust at middle to lower crustal depths is their main petrogenesis.

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Section: Geological Setting and Samplingsmentioning

confidence: 96%

Middle to Late Ordovician flare‐up of granitoids, South Altyn Tagh: Reworking of exhumed continental crust

Zhou,

Zhao,

Yao

et al. 2024

Geological Journal

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“…The outcropping sediments of the tectonic units situated in front of the Altyn fault zone are composed mainly of Jurassic, Paleogene, Neogene, and Quaternary strata (Figure 1). Further north, the basements that include granite, diorite, monzonite, syenite, and basaltic tuff were intruded by the Datonggou and Caishiling plutons [57,58].…”

Section: Geological Settingmentioning

confidence: 99%

Insights into the Weathering Crust Reservoirs of Granitoids: A Case Study from Qinghai Oilfield of Qaidam Basin, Northwest China

et al. 2022

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With proven reserves of 9.836 × 1010 m3, the largest known natural gas reservoir among terrigenous basement rocks has been discovered within the granitoids of the northern Qaidam Basin. Due to their high heterogeneity, the genesis of basement reservoirs remains unknown. Herein, the structure of the weathering crust in granitoids and their potential controlling factors on the reservoir development mechanism are discussed using a multidisciplinary approach based on data from cores, thin sections, scanning electron microscopy (SEM), conventional and imaging logs, and physical property and major elements analyses. Moreover, the classification standard of the weathering crust structure is established. The dissolution belt holding diverse reservoir spaces accounts for more than 50% of the total porosity, while the disintegration belt is the main context for the development of cleavage fractures and crack fractures. The original pores exist mainly among the crystal grains of quartz and mica, while the secondary pores and fractures were generated by the alteration of aluminosilicate minerals as well as biotite or hornblende. The quality of these reservoirs is controlled by their mineral composition, tectonic uplift, faulting, and paleogeomorphology. The femic granitoid is the main reservoir-forming lithology in the case of dissolution, while the felsic granitoid is more likely to develop cracks. The formation of the disintegration belt is significantly linked to the presence of faulting. These belts were mostly induced by tectonic deformation along the Altyn fault belt from the late Oligocene to the early Miocene. The diversity in paleogeomorphology influences the extent of the weathering. The exhumation in the Altyn terrane from the late Jurassic to the Cenozoic corresponds to the weathering and hypergene leaching period of the weathering crust within granitoids. Three types of reservoirs are present in the rocks: fractured-porous (Type Ⅰ); porous (Type Ⅱ); and fractured (Type Ⅲ). The fractured-porous and fractured reservoirs were developed mainly in the granitic gneiss and granite, while the porous reservoir was formed in granitic diorite and granitic gneiss. The reservoirs that developed in the weathering crust of granitoids are dominated by Type Ⅰ and Type Ⅱ. The highest quality reservoir, which is the fractured-porous type, developed mainly in the dissolution belt of the weathering crust, and has a porosity ranging from 1.56% to 8.48% and a permeability ranging from 0.03 mD to 14.48 mD. The mechanisms of the development of weathering crust reservoirs provide further information for the hydrocarbon exploration of basement rocks worldwide.

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Central China Orogenic Belt and amalgamation of East Asian continents

et al. 2021

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Origin and tectonic implications of granitoids from the eastern segment of the South Altyn Block, North‐western China: Constraints from petrogeochemistry, zircon U–Pb dating, and Lu–Hf isotope geochemistry

Cited by 4 publications

References 80 publications

Middle to Late Ordovician flare‐up of granitoids, South Altyn Tagh: Reworking of exhumed continental crust

Middle to Late Ordovician flare‐up of granitoids, South Altyn Tagh: Reworking of exhumed continental crust

Insights into the Weathering Crust Reservoirs of Granitoids: A Case Study from Qinghai Oilfield of Qaidam Basin, Northwest China

Central China Orogenic Belt and amalgamation of East Asian continents

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