Jian-Guo Yuan

China Geological Survey

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Huafeng Zhang

Xiamen Blood Center

Ying Tong

Chinese Academy of Geological Sciences

Lei Guo

Second Affiliated Hospital & Yuying Children's Hospital of Wenzhou Medical University

Jianfeng Gao

Chinese Academy of Sciences

Xinxia Geng

Chinese Academy of Geological Sciences

Rui‐Bin Liu

Chinese Academy of Geological Sciences

Tao Wang

Chinese Academy of Geological Sciences

Ying Tong

Chinese Academy of Geological Sciences

Xiao Rong-ge

Xi'an Shiyou University

Peng Song

Huazhong Agricultural University

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Chinese Academy of Geological Sciences

Ministry of Natural Resources

Peking University

Chinese Academy of Sciences

China University of Geosciences (Beijing)

Czech Academy of Sciences, Institute of Geology

Mineral Resources

Institute of Geochemistry

University of Hong Kong

Institute of Ecology and Geography

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Partial melting of thickened lower crust in the intraplate setting: constraints from triassic postectonic baishandong granitic pluton in Eastern Tianshan

International Geology Review (2022)

Jian-Guo Yuan Ying Tong Huafeng Zhang Xinxia Geng

Thickened crust is of great significance for tectonic evolution and mineralization and generally occurs in collisional orogenic belts. Whether accretionary orogenic belts, such as the Central Asian Orogenic Belt (CAOB), are able to create remarkably thickened crusts and what the mechanism is, remain to be determined. In the southwestern of CAOB, the Eastern Tianshan with broad magmatism and integrated arc-continental system is an excellent area for understanding the crustal evolution. Here, we report geochronological, geochemical and Nd-Hf-O isotope data for Middle Triassic Baishandong granites in the Eastern Tianshan, which exhibit three stages: Group 1 (ca. 237 Ma) granodiorites, Group 2 (ca. 234 Ma) monzogranites, and Group 3 (ca. 229 Ma) highly fractionated I-type granites. The Group 1 and 2 granites exhibit high-K, calc-alkaline, and metaluminous characteristics, weak negative Eu anomalies, and low (K2O+Na2O)/CaO and FeOT/MgO ratios with high Na2O/K2O, Sr/Y, and (La/Yb)N values and low MgO, Y, and Yb contents, which are indicative of adakitic affinity. The Group 3 rocks have extremely high SiO2 contents, notable Eu and Sr depletions, lower Mg# values, and the 'tetrad effect' of REEs, indicating that they are highly fractionated I-type granites. All the granites have similar depletion in Sr, Nd, Hf, and O isotope compositions (εNd(t) = 3.1–5.5, (87Sr/86Sr)i = 0.7036–0.7051, εHf(t) = 11.3–13.4, δ18O = 6.61–7.21) with young Nd, Hf second-stage model age (565–755 Ma, 425–541 Ma). It indicates that they are all the remelting of thickened juvenile lower crust that was initially derived from Neoproterozoic crust-mantle differentiation. Based on the discussion, we proposed that the granitic pluton intruded in an intraplate extensional setting, which indicates that thickened crust had existed before the Triassic and that the final amalgamation of the Paleo-Asian Ocean occurred in late Palaeozoic. Geochemical features indicate tectonic compression played a more important role in significant lower crust thickening.

Continental arc

10.1080/00206814.2022.2042861

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Hf isotopic mapping of the Paleozoic-Mesozoic granitoids from the Jiamusi and Songnen blocks, NE China: Implications for their tectonic division and juvenile continental crustal growth

Lithos (2021)

Maohui Ge Long Li Tao Wang Jinjiang Zhang Ying Tong

10.1016/j.lithos.2021.106048

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Sources of metals and fluids for the Taijiying gold deposit on the northern margin of the North China Craton

Ore Geology Reviews (2021)

Jian-Guo Yuan Huafeng Zhang Ying Tong Jianfeng Gao Xiao Rong-ge

• The fault-controlled Taijiying gold deposit was formed by four mineralization stages. • Ore-forming fluids of Taijiying were mainly magmatic water with minor meteoric water. • The ore-forming materials were mainly from magmas of partial melting of lower crust. • Triassic intrusions with developed fault systems might be gold prospective target. Recognition of the sources of metals and fluids is crucial to determine the genesis of gold deposits, especially in distinguishing the orogenic and magmatic hydrothermal deposits. There is no consensus on the source and genetic style of the Mesozoic gold deposits in the North China Craton (NCC). The Taijiying gold deposit in the Chifeng-Chaoyang gold district on the northern margin of the NCC is a medium-sized gold deposit and worth studying for its sources of metals and fluids. It is hosted by amphibole- to granulite-facies metamorphic rocks and Mesozoic intrusions, and controlled by NNE-, NE-trending compressional reverse faults and NW-trending extensional normal faults. The gold mineralization types include auriferous quartz veins and wall rock alterations of phyllic mineralization, pyritization, chloritization, and carbonatization. According to the crosscutting relationships of the veins and the mineral textures within the ore-bearing veins, four mineralization stages are recognized: clouded-white quartz ± pyrite (stage I), gray quartz + pyrite (stage II), quartz + polymetallic sulfides (stage III), and calcite ± quartz (stage IV), among which the stages II and III represent the main gold mineralization stages. The timing of the gold mineralization is constrained to the Middle Triassic by zircon U-Pb ages of a pre-metallogenic diorite (258.0 ± 1.9 Ma) and a ore-related granitic porphyry dike (241.5 ± 2.2 Ma). Three types of fluid inclusions (FIs) in the quartz veins of four stages are identified: vapor-rich (type 1), CO 2 -H 2 O three-phase (type 2), and liquid-rich FIs (type 3). Their trapping temperatures gradually decrease from 352 ℃ (stage I) to 124 ℃ (stage IV), with salinities decreasing from 9.8 to 2.0 wt% NaCl eqv., indicating that the ore-forming fluids belong to a H 2 O-NaCl-CO 2 system. The first three stages were characterized by moderate-high temperatures, a large variation in salinities, akin to those of the magmatic hydrothermal fluids. The H-O isotope compositions from the stage II (δ 18 Ow = 4.1–4.8‰ and δD = -110 to −87‰) to the stage III (δ 18 Ow = 3.5 to 3.7‰ and δD = -101 to −98‰), indicate that the ore-forming fluids were mainly magmatic fluids. The δ 34 S V-CDT (1.7–2.1‰), Pb isotopes ( 206 Pb/ 204 Pb = 15.09–15.90, 207 Pb/ 204 Pb = 15.00–15.15, 208 Pb/ 204 Pb = 35.76–37.97), and Os isotopes (initial 187 Os/ 188 Os = 2.3 ± 1.0) of the Au-bearing pyrite samples at the stages II and III, similar to those of the crust-derived magma, suggest that the gold and other metals were extracted from the partial melting of the lower crust. Accordingly, the Taijiying gold deposit is probably a magmatic hydrothermal deposit. The areas recording the Triassic batholith with a developed fault system would be prospective targets for gold mineralization in the Chifeng-Chaoyang district on the northern margin of the NCC.

Margin (machine learning)

Ore genesis

10.1016/j.oregeorev.2021.104593

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Contrasting Sources and Related Metallogeny of the Triassic and Jurassic Granitoids in the Chifeng–Chaoyang District, Northern Margin of the North China Craton: A Review with New Data

Minerals (2022)

Jian-Guo Yuan Huafeng Zhang Ying Tong Yun-Yan Qu Rui‐Bin Liu

Understanding of the mechanism between magma sources and metallogeny is still vague. As an important gold and molybdenum producing area, the Chifeng–Chaoyang district, located at the northern margin of the North China Craton (NCC), is a key place for this issue. New geochemical data relating to Taijiying gold-deposit-related granites are presented. These data, coupled with previous studies, are used to explore the relationship between magma sources and mineralization processes. Two major magmatic periods, the Middle Triassic (220–230 Ma) and Late Jurassic (150–160 Ma), are identified based on the compiled data. The Triassic magmatic rocks are mostly fractionated I-type and A-type granites, including monzogranite, biotite granite, and syenogranite. They have low initial 87Sr/86Sr values (0.7050), moderately enriched εNd(t)–εHf(t) values (−8.5 and −5.6), and relatively young Nd–Hf model ages (TDM2-TDMC) (1.47–1.57 Ga). These features indicate that more Archean–Paleoproterozoic mantle-derived materials were involved in their sources. On the other hand, Jurassic granites are high-K calc-alkaline of the calc-alkaline series and mainly consist of granite, monzogranite, leucogranite, and granodiorite. They have high Na2O/K2O, Sr/Y, and La/Yb ratios and low Y and Yb contents. The adakitic features suggest the existence of a thickened lower crust. Their significant negative εNd(t)–εHf(t) values (−15.0 and −12.8) and older Nd–Hf model ages (TDM2–TDMC) (2.17–2.11 Ga) are consistent with their derivation from thickened ancient lower crust, indicating the initial activation of NCC. It is proposed that the change in the main source resulted from the tectonic transition during the early Mesozoic initial decratonization, that is, from the post-collisional extension to the subduction of the Paleo-Pacific plate beneath the East Asia plate from the Triassic to the Jurassic. Comparative analysis suggests that the medium–large-scale gold deposits with a high grade are closely related to the Triassic granites; however, most molybdenum deposits formed in the Jurassic. The decratonization of the NCC in the early Mesozoic experienced tectonic transition and controlled the gold and molybdenum mineralizations in the different stages by the changing magma sources. This pattern is beneficial to understanding the metallogenesis in the Chifeng–Chaoyang district.

Metallogeny

10.3390/min12091117

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Citations (1)