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Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 24682

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Special Issue Editors

Dr. Ruibao Li

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Guest Editor

School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
Interests: ophiolite; granites; geochemistry; tectonics
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Xianzhi Pei

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Guest Editor

School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
Interests: field geology; tectonics; structure geology; geochemistry

Prof. Dr. Zuochen Li

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Guest Editor

School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
Interests: mineral; geological mapping; geochemistry

Dr. Lei Pei

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Guest Editor

School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
Interests: granites; geochemistry; structure geology

Dr. Guochao Chen

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Guest Editor

School of Civil Engineering, Nanyang Institute of Technology, Nanyang 473004, China
Interests: mineral geochemistry; granites; zirzon geochronology

Special Issue Information

Dear Colleagues,

The Qinghai–Tibet Plateau is Earth’s broadest and highest collisional system. Kunlun Orogen, located in the northern margin of the Qinghai–Tibet Plateau, recorded its early oceanic–continental tectonic evolutionary history. In particular, it incorporated at least two major tectonic events, including the tectonic processes of the Proto-Tethys Ocean in the Early Paleozoic and the Paleo-Tethys Ocean in the Late Paleozoic–Early Mesozoic. These events also record a history of Gondwana dispersal and Laurasian accretion. Thus, Kunlun Orogen provides a natural laboratory for studying not only ophiolites and subduction/collisional-type granitoids but also the evolutionary details of the Proto- and Paleo-Tethys ocean in north Gondwana.

Ophiolitic mélanges commonly occur in the collisional and accretionary orogens and are considered to be the indicators of the paleo-oceanic basin. Recent work has suggested that ophiolites can be classified into subduction-unrelated types and subduction-related types. These distinct ophiolites can be used to study the evolutionary details of the Paleo Ocean. Furthermore, granites mostly cropping out in the convergent plate margin record the subduction processes of the oceanic lithosphere and the collisional history of plates. In addition, granites are a key object for studying continental crustal growth based on their geochemical and isotopic composition. Thus, the study of ophiolites, granites, and even their spatio-temporal relationships become more necessary for reconstructing the detailed tectonic history of the Proto- and Paleo-Tethys Ocean in north Gondwana. In recent years, although the general tectonic framework and evolution history of these oceans have been restored, some debate still continues, mainly including (1) when the Proto-Tethys Ocean closed; (2) when the Paleo-Tethys Ocean began to subduct; (3) when the Qiangtang terrane collided with the consolidated Kunlun–Qaidam terrane and then docked to the southern margin of Laurasia; (4) how the continental crust grew and what the crust growth mechanism is; and (5) the magmatic evolutionary processes of voluminous granitic magmatism in Kunlun and the adjacent area.

The Special Issue aims to publish the new whole-rock/mineral geochemical and geochronological data from the northern Tibetan Plateau (Kunlun Orogen). We invite original research papers, reviews, and other contributions that are relevant to this issue.

Dr. Ruibao Li
Prof. Dr. Xianzhi Pei
Prof. Dr. Zuochen Li
Dr. Lei Pei
Dr. Guochao Chen
Guest Editors

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Keywords

ophiolitic mélange
granitic magmatism
geological evolution of Kunlun Orogen
geochemical and isotope constraints
Proto- and Paleo-Tethys Ocean

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Published Papers (12 papers)

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19 pages, 9987 KiB

Open AccessArticle

Zircon U-Pb Age and Geochemistry of Yamusi Granodiorite in the Eastern Part of the Qilian Orogen, China

by Lei Pei, Xianzhi Pei, Yu Zhang, Ruibao Li, Youxin Chen, Zuochen Li, Chengjun Liu and Meng Wang

Minerals 2023, 13(5), 677; https://doi.org/10.3390/min13050677 - 15 May 2023

Viewed by 1211

Abstract

Yamusi granodiorite in the eastern part of the Qilian Orogen consists mainly of gneissic granodiorite. Researchers have studied other nearby rock masses, and many studies, such as those focusing on the zircon U-Pb age chronology and geochemistry of Yamusi granodiorite, still need to be completed. We obtained a new LA–ICP–MS zircon U-Pb age of 480.3 ± 1.3 Ma for Yamusi granodiorite, which suggested that it was formed during the early Ordovician period. The whole-rock geochemical data show that this granodiorite is relatively rich in Na and poor in K (K₂O/Na₂O = 0.40–0.73). The granodiorite is metaluminous–weakly peraluminous and can be classified as medium-K calc-alkaline granite. It yields high Sr/Y ratios (35.17–53.78) and low Yb (<18 ppm) and Y (1.8 ppm) contents, an Mg# value of <45, and high La/Y ratios (2.9–13.4, mean = 5.76). The trace element compositions of the granodiorite are characterized by positive large-ion lithophile elements (LILEs; e.g., Cs, Rb, and Ba) and negative high-field-strength element (HFSE; e.g., Nb, Ta, and Ti) anomalies, similar to arc magmatic rocks. There is clear fractionation between the light and heavy rare earth elements (REEs), with (La/Yb)_N ratios of 1.77–9.03 (mean = 3.88). The petrogenesis research suggests that the granodiorite originated mainly from the partial melting of the mafic lower crust, with a minor mantle-derived component. Based on the regional geological setting, we suggest that the Yamusi granodiorite was formed during the northward subduction of the Proto-Tethyan oceanic crust to form an intracontinental arc. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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15 pages, 9929 KiB

Open AccessArticle

Zircon U–Pb Dating and Geochemical Characteristics of Chahannuo Gabbros in the Northern Margin of Qaidam Basin, Northern Tibetan Plateau

by Wei Du, Lei Pei, Ruibao Li, Zuochen Li, Chengjun Liu, Mao Wang, Hao Lin and Xianzhi Pei

Minerals 2023, 13(5), 651; https://doi.org/10.3390/min13050651 - 9 May 2023

Cited by 2 | Viewed by 1463

Abstract

Late Paleozoic–early Mesozoic intrusive rocks are distributed widely along the northern margin of the Qaidam Basin in the northern Tibetan Plateau. To constrain the tectonic evolution, we carried out petrological, chronological, and geochemical studies of the Chahannuo gabbros. LA-ICP-MS Zircon U–Pb dating yields an age of 255.0 ± 0.9 Ma for the gabbros, which confirms the existence of Indosinian tectono-magmatic activity on the northern margin of the Qaidam Basin. The Chahannuo gabbros have low whole-rock SiO₂, Fe₂O₃ contents, and high Al₂O₃ contents, which suggests a calc-alkaline affinity. In addition, the gabbros have high MgO, Cr, and Ni contents and Mg^#, similar to those predicted of the regional basaltic melts, and indicating that they were affected mainly by fluid from the subducted slab. The Chahannuo gabbros are characterized by arc-like trace element patterns, with enrichment in LREE and LILE, and depletion in HREE and HFSE. No obvious negative Eu anomalies also indicate that no significant magmatic differentiation has occurred. The low Nb/La ratio and Ti content in gabbros samples suggests that the Chahannuo gabbros were partially contaminated by the crust during their formation. The Chahannuo gabbros have high incompatible element ratios (Rb/Sr, Th/Nd, and Th/La), which are closer to the category of enriched mantle. Combing our data with previous data from contemporaneous magmatism in the region, we suggest that the Chahannuo gabbros formed in a continental arc environment related to the northward subduction of the Paleo-Tethyan oceanic plate. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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17 pages, 7962 KiB

Open AccessArticle

Petrogenesis and Tectonic Significance of Late Triassic A₁-Type Granite from the West Section of North Qinling Orogenic Belt: Constraints from Geochronology and Geochemistry

by Shang Ji, Zuochen Li, Xianzhi Pei, Lei Pei, Ruibao Li, Chengjun Liu, Youxin Chen, Hao Lin and Mao Wang

Minerals 2023, 13(4), 557; https://doi.org/10.3390/min13040557 - 16 Apr 2023

Cited by 2 | Viewed by 1637

Abstract

The North China Block and the South China Block collided in the Middle Triassic, but there is still a lack of consensus regarding the end of collisional orogeny and the closure time of the Paleo-Tethys. In this paper, we report zircon U–Pb ages and geochemistry for the Shimen pluton in the northern margin of the West Qinling Orogenic Belt to investigate its genesis and tectonic environment. The new findings allow to constrain the end time of the Triassic orogeny in the Qinling Orogenic Belt and the closure time of the Paleo-Tethys. The weighted average ²⁰⁶Pb/²³⁸U ages of the Shimen pluton are 218.6 ± 1.5 Ma and 221.0 ± 1.7 Ma. Thus, we suggest that the Shimen pluton crystallized at the 218.6 Ma and 221.0 Ma and was formed during the Late Triassic (Norian). The Shimen pluton is mainly syenogranite and has alkaline dark minerals aegirine–augite. It is composed of 73.45 to 77.80 wt.% SiO₂, 8.28 to 9.76 wt.% alkali, and 11.35 to 13.58 wt.% Al₂O₃, with A/CNK ranging from 0.91 to 1.02 and 10,000 Ga/Al ranging from 2.39 to 3.15. These findings indicate that the Shimen pluton is typical A-type granite. The plutons have low rare earth element contents, ranging from 73.92 to 203.58 ppm, with a moderate negative Eu anomaly. All the samples are enriched in large-ion lithophile elements, such as Rb, Nd, Th and U, and light rare earth elements, and are depleted in high field strength elements, such as Nb, P, Zr, Ba, and Sr. The depletion of Ba, Sr, and Zr may be related to the fractionation and evolution of the granite. According to the petrological and geochemical characteristics, the Shimen pluton is an A₁-type granite formed in an anorogenic extensional environment. Combined with its tectonic characteristics and petrogenesis, the Shimen pluton was probably formed by the partial melting of the crust under high temperature and low pressure in the intraplate environment after the subduction of the South China Block beneath the North China Block. This observation indicates that the Triassic orogeny in the Qinling Orogenic Belt had ended and the Paleo-Tethys-Mianlve Ocean had also closed by the Late Triassic (Norian). Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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26 pages, 8815 KiB

Open AccessEditor’s ChoiceArticle

Timing of Transition from Proto- to Paleo-Tethys: Evidence from the Early Devonian Bimodal Volcanics in the North Qaidam Tectonic Belt, Northern Tibetan Plateau

by Mao Wang, Xianzhi Pei, Ruibao Li, Lei Pei, Zuochen Li, Chengjun Liu, Lili Xu and Hao Lin

Minerals 2023, 13(4), 532; https://doi.org/10.3390/min13040532 - 10 Apr 2023

Cited by 2 | Viewed by 1870

Abstract

The transition from the Proto- to the Paleo-Tethys is still a controversial issue. This study reports a new petrology, zircon U–Pb geochronology, and whole-rock geochemistry of volcanic rocks from the Maoniushan Formation in the Nankeke area, northern Qaidam (NQ) of the Tibetan Plateau, to provide new evidence for the transition from the Proto- to the Paleo-Tethys oceans. The volcanic suite consists mainly of rhyolitic crystal lithic tuff lavas and minor basalts. Zircon U–Pb data indicate that the bimodal volcanic rocks were formed during the Early Devonian (ca. 410–409 Ma). Geochemically, the basalts have low contents of SiO₂ (48.92 wt.%–51.19 wt.%) and relatively high contents of MgO (8.94 wt.%–9.99 wt.%), TiO₂ (1.05 wt.%–1.29 wt.%), K₂O (2.35 wt.%–4.17 wt.%), and K₂O/Na₂O ratios (1.04–2.56), showing the characteristics of calc-alkaline basalts. Their rare earth element (REE) patterns and trace element spider diagrams are characterized by enrichments in LREEs (LREE/HREE = 18.31–21.34) and large ion lithophile elements (LILEs; Rb, Th, and K) and depletion in high-field-strength elements (HFSEs; Nb, Ta, P, and Ti), with slight negative Eu anomalies (Eu/Eu* = 0.82–0.86), which are similar to Etendeka continental flood basalts (CFB). These features suggest that the basalts were most likely derived from low degree (1%–5%) partial melting of the asthenospheric mantle, contaminated by small volumes of continental crust. In contrast, the felsic volcanics have high SiO₂ (68.41 wt.%–77.12 wt.%), variable Al₂O₃ (9.56 wt.%–12.62 wt.%), low MgO, and A/CNK ratios mostly between 1.08 and 1.15, defining their peraluminous and medium-K calc-alkaline signatures. Their trace element signatures show enrichments of LREEs and LILEs (e.g., Rb, Th, U, K, and Pb), depletion of HFSEs (e.g., Nb, Ti, Ta, and P), and negative Eu anomalies (Eu/Eu* = 0.22–0.66). These features suggest that the felsic volcanics were derived from partial melting of the middle crust, without interaction with mantle melts. Considering all the previous data and geochemical features, the Maoniushan Formation volcanic rocks in NQ formed in a post-collisional extensional setting associated with asthenospheric mantle upwelling and delamination in the Early Devonian. Together with the regional data, this study proposed that the Proto-Tethys Ocean had closed and evolved to the continental subduction/collision orogeny stage during the Middle to Late Ordovician, evolved to the post-collisional extensional stage in the Early Devonian, and finally formed the Zongwulong Ocean (branches of the Paleo-Tethys Ocean) in the Late Carboniferous, forming the tectonic framework of the Paleo-Tethys Archipelagic Ocean in the northern margin of the Tibetan Plateau. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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16 pages, 4058 KiB

Open AccessArticle

Tectono-Magmatic Significance of the Lower Devonian Mafic Intrusions in the East Kunlun Orogenic Belt: Keys for the Evolution of Proto-Tethys

by Yong Meng, Xin Zhang, Zuochen Li, Yuan Han, Haibo Zhao, Yang Yang and Xingchen Xu

Minerals 2023, 13(4), 478; https://doi.org/10.3390/min13040478 - 28 Mar 2023

Viewed by 1835

Abstract

Studies on post-collisional magmatic rocks can provide key clues to researching the crust–mantle interactions and the tectonic evolution of collisional orogenic belts. This study investigated a suite of newly discovered mafic intrusions in the middle of the East Kunlun orogenic belt through integrated analysis of petrology, petrography, and zircon U–Pb dating. The data could offer new insights into the generation of the Proto-Tethyan tectonic evolution. The result shows that these mafic intrusions are mainly gabbro and diabase, formed in the Early Devonian, with zircon U–Pb ages of 408.9 ± 2.0 Ma for gabbro and 411.1 ± 3.1 Ma for diabase. It consists of plagioclase, pyroxene, and dark minerals, and a small number of calcite and chlorite. Diabase has a small amount of amygdale. Their Na₂O + K₂O contents range from 3.47 wt.% to 5.45 wt.%, with Na₂O/K₂O ratios from 1.39 to 3.09, suggesting that they are calc–alkaline rocks. These rocks have an Fe₂O₃ᵀ content of 7.68 wt.%–11.59 wt.% and Mg^# of 50.58–59.48, belonging to the iron-rich and magnesium-poor type. The chondrite-normalized rare earth elements show similar patterns that are characterized by enrichment of light rare earth elements, with (La/Yb)_N of 3.27–6.75 and no significant europium anomaly, indicating the rocks are homogenous. The studied rocks are characterized by low contents of compatible elements Cr and Ni, enrichment of large-ion lithophile elements such as Rb, U, Sr, and Nd, and high-field-strength elements such as Nb, Ta, Zr, Hf, and Th. The mafic magma originated from the partial melting of the enriched mantle and was assimilated and mixed with crust materials during the process of migration. Based on the regional tectonic evolution, we interpret that the Proto-Tethys Ocean had closed in the Early Devonian, and that the East Kunlun region was in a post-collisional extensional tectonic setting. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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19 pages, 48291 KiB

Open AccessArticle

Petrogenesis of the Ore-Related Intrusions of the Aikengdelesite Mo (–Cu) and Halongxiuma Mo Deposits: Implication for Geodynamic Evolution and Mineralization in the East Kunlun Orogen, Northwest China

by Qinglin Xu, Yonggang Sun, Guangzhou Mao, Wei Xin and Yanqian Yang

Minerals 2023, 13(3), 447; https://doi.org/10.3390/min13030447 - 22 Mar 2023

Cited by 1 | Viewed by 1873

Abstract

The East Kunlun Orogenic Belt (EKOB) is the most important Triassic polymetallic metallogenic belt in China. A study about the petrogenesis of the ore-related intrusions is of great significance to the geodynamic evolution of orogenic belts. In this study, analysis of U–Pb zircon dating, whole-rock major and trace element compositions, and zircon Hf isotopes for the granitoids hosting the Aikengdelesite Mo (–Cu) and Halongxiuma Mo deposits in the EKOB are studied to determine their chronology and petrogenesis. Zircon date results show that the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry formed at 244.2 ± 1.7 Ma and 230.0 ± 1.0 Ma respectively. All samples of the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry which have high SiO₂ and K₂O contents, and low MgO and Cr, belong to the high-K calc-alkaline series. The Aikengdelesite granite porphyry samples show I-type geochemical affinities, whereas the Halongxiuma granodiorite porphyry samples are A-type granitoids. They all show negative zircon ε_Hf(t) values (−7.4 to −3.3 and −3.7 to −2.5). We suggest that the Aikengdelesite granite porphyry may have been derived from the lower continental crust. While the Halongxiuma granodiorite porphyry could have formed by partial melting of basic lower crustal materials. By combining the results of this study with previous data, two magmatic and mineralization peak periods (278–237 Ma and 230–210 Ma) were observed in the Paleo-Tethys of the EKOB. Porphyry–skarn deposits occurring in the first episode were formed in the setting of an active continental margin related to the Paleo-Tethys Ocean plate subduction (e.g., Aikengdelesite porphyry deposit), while deposits occurring in the second episode were formed in a post-collisional setting (e.g., Halongxiuma porphyry deposit). Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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19 pages, 4622 KiB

Open AccessEditor’s ChoiceArticle

Tectonic Background of Carboniferous to Early Permian Sedimentary Rocks in the East Kunlun Orogen: Constraints from Geochemistry and Geochronology

by Xiao Wang, Xianzhi Pei, Ruibao Li, Chengjun Liu, Lei Pei, Zuochen Li, Youxin Chen and Meng Wang

Minerals 2023, 13(3), 312; https://doi.org/10.3390/min13030312 - 23 Feb 2023

Viewed by 2496

Abstract

The formation of the East Kunlun Orogen (EKO) was related to the tectonic evolution of the Proto-Tethys and Paleo-Tethys Oceans. However, how the Paleo-Tethys Ocean transited from the Proto-Tethys Ocean, and whether the Paleo-Tethys Ocean subducted northward beneath the East Kunlun–Qaidam Terrane in Carboniferous to Permian times, is still highly debated. Early Carboniferous Halaguole and Late Carboniferous to Early Permian Haoteluowa formations are extensively outcropped in the EKO, north Tibetan Plateau, and have thus recorded key information about the tectonic processes of the Paleo-Tethys Ocean that have implications for the reconstruction of the Northern Paleo-Tethys Ocean (Buqingshan Ocean). Siliciclastic rocks within these formations are collected for petrogeological, geochemical, and detrital zircon U–Pb dating research. Our results show that sandstones from Halaguole and Haoteluowa formations have an average total quartz–feldspar–lithic fragment ratio of Q₆₇F₁₂L₂₁ and Q₅₀F₂₀L₃₀, respectively, indicating relatively high compositional maturity. The geochemical results suggest that the average values of the Chemical Index of Alteration (CIA) are 57.83 and 64.66; together with their angular to subangular morphology, this indicates that their source rocks suffered from weak weathering and the sandstones are the result of proximal deposition. Geochemical features such as the low La/Th, TiO₂, and Ni values suggest that the parental rocks in the provenance area are mainly acidic igneous rocks with minor intermediate igneous and old sedimentary components. The detrital zircon U–Pb age spectrum of these samples is dominated by age peaks at ~405–503 Ma and ~781–999 Ma, with subordinate age peaks at ~1610–2997 Ma and ~1002–1529 Ma, which show tectono–thermal events similar to those of the North Qimatag Belt (NQB), North Kunlun Terrane (NKT), and South Kunlun Terrane (SKT). These features suggest a contribution from the Early Paleozoic magmatic arc and Proterozoic basements in the NQB, NKT, and SKT to the Halaguole and Haoteluowa formations in these areas. In addition, the youngest zircon age of ~440 Ma from these sandstones is greater than the depositional age of Halaguole and Haoteluowa formations, which is a typical basin depositional feature in a passive continental margin. Geochemical tectonic discrimination diagrams, based on a major and trace element Ti/Zr–La/Sc plot, in combination with a detrital zircon age distribution pattern, all suggest a passive continental margin setting. Considering this together with the previous data, we argue that the Paleo-Tethys Ocean did not begin to subduct northward and that there was no oceanic subduction zone in the south EKO during Carboniferous to Early Permian times. Combining this information with that from previous studies suggests that the initial opening of the Paleo-Tethyan Ocean may have occurred before the Early Carboniferous time, and all the branches of the Paleo-Tethys Ocean constituted a complex ocean–continent configuration across parts of what is now Asia during the Early Carboniferous to Early Permian. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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20 pages, 8025 KiB

Open AccessEditor’s ChoiceArticle

Petrogenesis and Geochronology of A₁-Type Rhyolites in the Late Late Triassic of the East Kunlun Orogenic Belt: Constraints on the End of the Paleo-Tethys Orogenic Event

by Zuochen Li, Xianzhi Pei, Lei Pei, Chengjun Liu, Lili Xu, Ruibao Li, Hao Lin, Mao Wang, Shang Ji, Li Qin, Yajie Yang, Meng Wang, Shaowei Zhao and Youxin Chen

Minerals 2023, 13(2), 290; https://doi.org/10.3390/min13020290 - 18 Feb 2023

Cited by 2 | Viewed by 1851

Abstract

The rhyolites which are widely exposed to the northern margin of the East Kunlun orogenic belt were chosen as a research object to discern the post-orogenic tectonic evolution of the East Kunlun orogenic belt and reconstruct the post-collision orogenic processes of the Buqingshan- A’nyemaqen Ocean. We researched zircon U-Pb ages and geochemistry characteristics of the Late Triassic rhyolites in the eastern segment of the East Kunlun Orogenic Belt in the northern Tibetan Plateau. Zircon U-Pb dating yields coeval ages of 200.4 ± 1.4 Ma and 202.8 ± 1.2 Ma for the Keri rhyolites of the East Kunlun Orogenic Belt, indicating that the volcanic rocks were formed in the Late Triassic Rhaetian–Early Jurassic Hettangian. The Keri rhyolite is a product of the late magmatism of the Elashan Formation volcanic rocks. The rhyolites include rhyolitic brecciated tuff lavas and rhyolitic tuff lavas. The rhyolites are peraluminous and are high-K calc-alkaline, with high contents of SiO₂, K₂O, TFe₂O₃, and low P₂O₅ contents. The A/CNK ratios range from 0.97 to 1.09, indicating that the rhyolites are metaluminous to weakly peraluminous. The chondrite-normalized rare earth element (REE) distribution shows a significant negative Eu anomaly and low total REE concentrations. All samples are depleted in high field strength elements (HFSEs, e.g., Eu, Sr, Ti, and P), heavy rare earth elements (HREEs), and enriched in large ion lithophile elements (LILEs, e.g., Rb, Zr, Nd, Th, and U) and light rare earth elements (LREEs). The Keri rhyolite has the characteristics of A₁-type magmatic rock, formed in an anorogenic environment after the closure of the Paleo-Tethys Ocean, and was the product of late magmatism in the Elashan Formation volcanic rocks. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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23 pages, 7937 KiB

Open AccessArticle

Contribution of Triassic Tectonomagmatic Activity to the Mineralization of Liziyuan Orogenic Gold Deposits, West Qinling Orogenic Belt, China

by Shuo Wang, Zhanjin Liu, Yunhua Liu, Nan Deng, Benzhao Yang and Le Tan

Minerals 2023, 13(1), 130; https://doi.org/10.3390/min13010130 - 16 Jan 2023

Cited by 7 | Viewed by 2240

Abstract

The Western Qinling orogenic belt (WQOB) is one of the most important prospective gold districts in China, with widely distributed Indosinian intermediate–acidic intrusions. The Liziyuan Au deposit is a representative orogenic deposit in the northern WQOB, hosting several sections spatially associated with igneous rocks. The Au deposit is hosted by meta-sedimentary volcanic rocks of the Cambrian–Ordovician Liziyuan Group and the Tianzishan monzogranite. Two periods, including five stages of mineralization, are recognized in this area: an early metamorphic mineralization period (PI), including quartz–pyrite (Stage I) and banded quartz–polymetallic sulfide (Stage II) veins, and a later magmatic mineralization period (PII) including quartz–K-feldspar–pyrite–molybdenite veins (Stage III), quartz–polymetallic sulfide–chlorite ± calcite veinlets and stockwork (Stage IV), and late calcite–quartz veinlets (Stage V). Geochronological studies indicate a SHRIMP zircon U-Pb age of 236.1 Ma for the Tianzishan monzogranite, and our published ages of ore-bearing diorite porphyrite of the Suishizi section and granite porphyry of the Jiancaowan section being 213 and 212 Ma, respectively. Pyrites formed in association with PI and PII mineralization have well-defined Rb–Sr ages of 220 ± 7.5, 205.8 ± 8.7, and 199 ± 15 Ma, with close temporospatial coupling between mineralization and magmatism. The δ¹⁸O and δD values of fluid inclusions in Stage IV auriferous quartz veins range from −0.03‰ to +5.24‰ and −93‰ to −75‰, respectively, suggesting that mineralizing fluid was likely of magmatic origin. Three distinct ranges of δ³⁴S values are identified in the studied sections (i.e., 7.04‰–9.12‰, −4.95‰ to −2.44‰, and 0.10‰–3.08‰), indicating a source containing multiple sulfur isotopes derived from magmatic and metamorphic fluids. The Liziyuan Au deposit is thus likely an orogenic deposit closely related to magmatism. Geochemical characteristics indicate that Tianzishan monzogranite is adakitic and was derived from thickened lower crust during Triassic orogenesis. The ore-bearing diorite porphyrite and granite porphyry formed in a post-collision extensional setting. Together with previous geological and geochemical data, our results indicate that the Liziyuan orogenic Au deposit was formed by early collisional–compressional metamorphism and late post-collision extensional magmatic fluids related to the evolution of the WQOB. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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20 pages, 5166 KiB

Open AccessArticle

Petrogenesis of Middle Triassic Adakite-like Intrusions in the Asiha Orogenic Gold Deposit, East Kunlun Orogenic Belt, China

by Namkha Norbu, Ling Tang, Jinchao Li, Huilei Kong, Yazhi Li, Qunzi Jia and Yan Xu

Minerals 2023, 13(1), 74; https://doi.org/10.3390/min13010074 - 2 Jan 2023

Cited by 2 | Viewed by 1852

Abstract

The East Kunlun Orogenic Belt is considered as one of the important gold mineralization regions in the Tethys tectonic domain. These orogenic gold deposits are related to intermediate-acid intrusions formed at the end of Paleo-Tethys evolution, but the petrogenesis is controversial. This paper presents a new study on the geochemistry of zircon U-Pb, O, S, and Pb isotopic compositions of Asiha quartz diorite, granite porphyry, and sulfides. The geochemical features of quartz diorite and granite porphyry are consistent with the modern adakite, with high content of Sr but low content of Y, Yb, and MgO. Magmatic zircons from these two types of intrusion yielded U-Pb ages of 238.4 ± 1.4 Ma and 240 ± 1.7 Ma, respectively. The high O isotopic composition of Asiha complex may reflect that crust or crustal derivates were incorporated into the magmatic melt, and the Pb isotope characteristics indicates a lower crust origin. The δ³⁴S values of pyrites range from 4.9‰ to 11.6‰. This study infers that the Asiha complex perhaps formed by partial melting of the Paleo-Tethys subducted oceanic crust with seafloor sediments and is markedly different from the traditional adakite. Asiha deposit is an orogenic gold deposit related to adakite-like rocks, which formed in Triassic in the East Kunlun Orogenic Belt. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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23 pages, 5956 KiB

Open AccessArticle

Multiple Sources of Indosinian Granites and Constraints on the Tectonic Evolution of the Paleo-Tethys Ocean in East Kunlun Orogen

by Guochao Chen, Xianzhi Pei, Ruibao Li, Zuochen Li, Youxin Chen, Chengjun Liu and Lei Pei

Minerals 2022, 12(12), 1604; https://doi.org/10.3390/min12121604 - 14 Dec 2022

Cited by 7 | Viewed by 1836

Abstract

Numerous Indosinian granitoids occur in the East Kunlun Orogen (EKO). The Indosinian was a key transitional period associated with the evolution of the Paleo-Tethys Ocean. Here, we study the relationship between the petrogenesis of the granitoids and the regional tectonic setting based on a comprehensive analysis of the petrology, geochronology, and geochemistry of typical granitoids in the eastern part of the EKO. The Indosinian granitoid compositions are dominated by quartz diorites, granodiorites, monzogranites, porphyritic monzogranites, and syenogranites. Early Indosinian granitoids are large, granitic batholiths, while the middle and late Indosinian granitoids are smaller in size. From the early Indosinian to late Indosinian, the granitoids show a transition from a medium-K calc-alkaline to high-K calc-alkaline composition. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) and depleted in high-field-strength elements (HFSEs), especially for the Helegangxilikete and the Kekeealong plutons. The late Indosinian granitoids have relatively low Y and Yb contents, high Sr contents, and high La/Yb and Sr/Y ratios, which suggests adakitic affinity. The zircon saturation temperatures of the early Indosinian syenogranite and the Keri syenogranite are above 800 °C. The zircon saturation temperatures of other Indosinian granites (average 749 °C) are lower than those of the biotite and amphibole partial melting experiment. In the early Indosinian (255–240 Ma), numerous granitoids were the products of the partial melting of the juvenile lower crust by mafic magma underplating. This underplating is geodynamically related to the continuous subduction of a branch of Paleo-Tethys Ocean, with slab break-off, rapid upwelling, and mantle decompression. In the middle Indosinian (240–230 Ma), the compression that accompanied the continent–continent collision was not conducive to fluid activity, and hence, the formation of magma could be attributed to dehydration partial melting of muscovite, biotite, or amphibole. In the late Indosinian (230–200 Ma), the delamination of thickened crust would provide heat and channels for fluid migration, leading to a flare-up of the magmas. The composition and petrogenesis of the Indosinian granitoids in the eastern EKO are the result of processes associated with the subduction, collisional, and post-collisional stages, during the evolution of the Paleo-Tethys Ocean. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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Review

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33 pages, 22485 KiB

Open AccessReview

Paleo-Tethyan Ocean Evolution and Indosinian Orogenesis in the East Kunlun Orogen, Northern Tibetan Plateau

by Ruibao Li, Xianzhi Pei, Zuochen Li, Lei Pei, Guochao Chen, Zhanqing Liu, Youxin Chen, Chengjun Liu, Meng Wang and Min Zhang

Minerals 2022, 12(12), 1590; https://doi.org/10.3390/min12121590 - 11 Dec 2022

Cited by 18 | Viewed by 3171

Abstract

The East Kunlun Orogen on the northern margin of the Tethyan orogenic system records a history of Gondwana dispersal and Laurasian accretion. Uncertainties remain regarding the detailed histories of northern branches of the Paleo-Tethys Ocean in East Kunlun Orogen (Buqingshan Ocean). Based on a synthesis of sedimentary, structural, lithological, geochemical, and geochronological data from the East Kunlun Orogen and adjacent regions, this paper discusses the spreading and northward consumption of the Paleo-Tethys Ocean during Late Paleozoic–Early Mesozoic times. The main evolutionary stages are: (1) during Carboniferous to Middle Permian, the Paleo-Tethys Ocean (Buqingshan Ocean) was in an ocean spreading stage, as suggested by the occurrence of Carboniferous MORB-, and OIB-type oceanic units and Carboniferous to Middle Permian Passive continental margin deposits; (2) the Buqingshan Ocean subducted northward beneath the East Kunlun Terrane, leading to the development of a large continental magmatic arc (Burhan Budai arc) and forearc basin between ~270–240 Ma; (3) during the late Middle Triassic to early Late Triassic (ca. 240–230 Ma), the Qiangtang terrane collided with the East Kunlun–Qaidam terranes, leading to the final closure of the Buqingshan Ocean and occurrences of minor collision-type magmatism and potentially inception of the Bayan Har foreland basin; (4) finally, the East Kunlun Orogen evolved into a post-collisional stage and produced major magmatic flare-ups and polymetallic mineral deposits between Late Triassic to Early Jurassic (ca. 230–200 Ma), which is possibly related to asthenospheric mantle upwelling induced by delamination of thickened continental lithosphere and partial melting of the lower crust. In this paper, we propose that the Wilson cycle-like processes controlled the Late Paleozoic–Early Triassic tectonic evolution of East Kunlun, which provides significant implications for the evolution of the Paleo-Tethys Ocean. Full article

(This article belongs to the Special Issue Petrology, Geochemistry and Isotopes of Ophiolite and Granites in Kunlun Orogen and Adjacent Area)

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