Zircon SHRIMP U-Pb ages and trace element geochemistry of the Kuhai gabbro and the Dur’ngoi diorite in the southern east Kunlun tectonic belt, Qinghai, Western China and their geological implications

Abstract

Timing of the intermediate-basic igneous rocks developed in the area of Kuhai-A'nyêmaqên along the southern east Kunlun tectonic belt is a controversial issue. This paper presents new zircon SHRIMPU-Pb dating data for igneous zircons from the Kuhai gabbro and the Dur'ngoi diorite in the Kuhai-A'nyemaqen tectonic belt, which are 555±9 Ma and 493±6 Ma, respectively. The trace element geochemical features of the Kuhai gabbro and the Dur'ngoi diorite are similar to those of ocean island basalts (OIB) and island arc basalts (IAB), respectively. Thus, the Kuhai gabbro with the age of 555±9 Ma and OIB geochemical features is similar to the Yushigou oceanic ophiolite in the North Qilian orogen, whereas the Dur'ngoi diorite with the age of 493±6 Ma and IAB geochemical features is similar to the island arc volcanic rocks developed in the north Qaidam. The Late Neoproterozoic to Early Ordovician ophiolite complex in the area of Kuhai-A'nyêmaqên suggests that the southern margin of the "Qilian-Qaidam-Kunlun" archipelagic ocean in this period was located in the southern east Kunlun tectonic belt. Therefore, the southern east Kunlun tectonic belt in the early Paleozoic is not comparable to the Mianlüe tectonic belt in the Qinling orogenic belt.

Early Ordovician island‐arc‐type Manite granodiorite pluton from the Buqingshan Tectonic Mélange Belt in the southern margin of the East Kunlun Orogen: constraints on subduction of the Proto‐Tethyan Ocean

“…This age is significantly later than that of the Buqingshan tectonic mélange Delisitan oceanic ridge ophiolite (gabbros aged 516.4 ± 6.3 to 467.2 ± 0.9 Ma; Bian et al ., ; Liu et al ., ), Majixueshan oceanic ridge ophiolite in the A'nyemaqen Tectonic Mélange Belt (535 ± 10 Ma) (Li et al ., ), Qingshuiquan ophiolite in the central eastern Kunlun Tectonic Mélange Belt (522.3 ± 4.1 to 507.7 ± 8.3 Ma) (Yang et al ., ; Lu et al ., ; Li et al ., ; Chen et al ., ; Ren et al ., ), and ancient ocean basin remnants of the Kekesha–Kekekete mafic–ultramafic mélange (509.4 ± 6.8 to 501 ± 7 Ma) (Feng et al ., ; Li et al ., ). This age is earlier than that of the Yikehalaer island‐arc granodiorite rock mass (437.5 ± 6.6 Ma to 402 ± 24 Ma; Bian et al ., ; Liu, ; Li et al ., ), the Bairiqiete island‐arc granodiorite (441.1 ± 6.3 Ma to 439.0 ± 1.9 Ma; Liu et al ., ; Li et al ., ), and acidic volcanic lava (437.7 ± 2.8 Ma; Liu et al ., ) in the Buqingshan–A'nyemaqen Early Palaeozoic Tectonic Mélange Belt, and similar to the Dur'ngoi island‐arc diorite age (493 ± 6 Ma; Li et al ., ). Finally, the post‐collision granitoids of the East Kunlun Orogen (411 ± 17 Ma to 394 ± 13 Ma; Liu et al , ; Zhao et al , ; Chen et al , ; Long et al , ), Helegangnaren A‐type granites of the north side of the East Kunlun Fault (425 ± 7 Ma, Li et al ., ), and the extension‐type molasse of the Maoniushan Formation in the north of East Kunlun Orogen and the northern margin of the Qaidam Basin (423.2 ± 1.8 Ma to 399.6 ± 2.8 Ma; Xu et al ., ; Li et al ., ; Lu et al ., ; Zhang et al , ) are significantly later than the Manite granodiorite.…”

“…Previous researches of the Early Palaeozoic magmatic rocks have shown that there are old island‐arc magmatic characteristics in the Buqingshan–A'nyemaqen Tectonic Mélange Belt (Bian et al ., , b; Liu, ; Liu et al ., , b). The ages of these magmatic rocks are divided into two phases: the early phase is the Cambrian–Furongian (such as De Dur'ngoi diorite; Li et al ., ), and the later phase is Early Silurian (such as Yikehalaer granodiorite, Bairiqiete granodiorite, and acidic volcanic lava; Bian et al ., ; Liu, ; Li et al ., , respectively). The formation ages of this Early Palaeozoic magmatic are similar to the subduction time of the Proto‐Tethyan Ocean.…”

Geochemistry, geochronology, and Hf isotope of diorites in the Marzheng area: Implications for the Early Palaeozoic tectonic evolution of the East Kunlun Orogenic Belt

“…The East Kunlun Orogenic belt (E‐KOB) located in the northern Tibetan Plateau and the western part of the Central China Orogenic Belt has witnessed the subduction–accretion process of the Proto‐ and Palaeo‐Tethys Ocean, and accordingly was suggested as an accretionary orogen (Figure 1a,b; Dong et al, 2021; Dong, He, et al, 2018; Li et al, 2016; Song et al, 2018). During the long‐term subduction–accretion process, a series of Tethys oceanic crust fragments—ophiolitic mélanges (Bian et al, 2001, 2002, 2004; Li et al, 2007; Liu, Pei, Li, Li, Chen, Gao, et al, 2011; Liu, Pei, Li, Li, Zhang, et al, 2011; Yang et al, 2009), as well as related magmatic rocks (Bian et al, 2007; Li et al, 2017; Li, Pei, Li, Pei, Liu, et al, 2014; Wei, Gan, Bao, et al, 2018; Wei, Gan, Cang, & Kang, 2018; Xiong et al, 2015) are well preserved in the southern margin of the E‐KOB (Figure 1b). The Muztagh‐Buqingshan‐Anemaqen ophiolitic mélange zone (MBAM) is situated in the southern margin of the East Kunlun Orogenic Belt and is characterized by widely distributed ophiolitic mélange and different types of intrusive rock in the Muztagh, Buqingshan, and Anemaqen areas with formation ages of ca.…”

“…AKM, Aqikekulehu–Kunzhong ophiolitic mélange zone; MBAM, Muztagh–Buqingshan–Animaqen ophiolitic mélange zone (modified after Dong, He, et al, 2018); QXM, Qimantagh‐Xiangride mélange zone. Age data are from (1) Wei, Gan, Bao, et al (2018); (2) Wei, Gan, Cang, and Kang (2018); (3) Li et al (2017); (4) Bian, Pospelov, Li, Chang, and Li (2007); (5) Li, Pei, Li, Pei, et al (2015); (6) Liu, Pei, Li, Li, Zhang, et al (2011); (7) Liu, Pei, Li, Li, Chen, Chen, et al (2011); (8) Bian et al (2004); (9) Wang (2015); (10) Li (2008); (11) Xiong, Ma, Wu, Jiang, and Liu (2015); (12) Li, Li, Guo, Sun, and Zhang (2007); (13) Yang, Shi, Wu, Wang, and Robinson (2009); (14) Liu et al (2013). (c) Simplified geological map showing sample location in Marzheng area…”

“…According to the previous study, the oldest ophiolites are outcropped in the Kuhai area with the geochemical characteristics of oceanic island basalts (OIB) and crystallized at 555 Ma (Li et al, 2007). In addition, most ophiolites show typical normal mid‐ocean ridge affinity with formation ages of ca.…”