Andesitic crustal growth via mélange partial melting: Evidence from Early Cretaceous arc dioritic/andesitic rocks in southern Qiangtang, central Tibet

2016 ◽  
Vol 17 (5) ◽  
pp. 1641-1659 ◽  
Author(s):  
Lu-Lu Hao ◽  
Qiang Wang ◽  
Derek A. Wyman ◽  
Quan Ou ◽  
Wei Dan ◽  
...  
Keyword(s):  
Partial Melting ◽  
Early Cretaceous ◽  
Crustal Growth ◽  
Central Tibet

Late early Cretaceous peraluminous biotite granites along the Bangong–Nujiang suture zone, Central Tibet: Products derived by partial melting of metasedimentary rocks?

Lithos ◽  
2019 ◽  
Vol 344-345 ◽  
pp. 147-158
Author(s):  
Wan-Long Hu ◽  
Qiang Wang ◽  
Jin-Hui Yang ◽  
Chunfu Zhang ◽  
Gong-Jian Tang ◽  
...  
Keyword(s):  
Partial Melting ◽  
Early Cretaceous ◽  
Suture Zone ◽  
Metasedimentary Rocks ◽  
Central Tibet

Early Cretaceous K-rich rhyolites from the Duolong Cu–Au deposit, southern Qiangtang, China: evidence for crustal growth

2017 ◽  
Vol 60 (9) ◽  
pp. 1098-1115 ◽  
Author(s):  
Wei Wang ◽  
Ming Wang ◽  
Cai Li ◽  
Jian-Jun Fan ◽  
Wei Xu ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Crustal Growth

Late Eocene post-collisional magmatic rocks from the southern Qiangtang terrane record the melting of pre-collisional enriched lithospheric mantle

2021 ◽  
Author(s):  
Yue Qi ◽  
Qiang Wang ◽  
Gang-jian Wei ◽  
Xiu-Zheng Zhang ◽  
Wei Dan ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Trace Element ◽  
Partial Melting ◽  
Early Cretaceous ◽  
Lithospheric Mantle ◽  
Late Eocene ◽  
The Tibetan Plateau ◽  
Mafic Rocks ◽  
Isotopic Compositions ◽  
Qiangtang Terrane

Diverse rock types and contrasting geochemical compositions of post-collisional mafic rocks across the Tibetan Plateau indicate that the underlying enriched lithospheric mantle is heterogeneous; however, how these enriched mantle sources were formed is still debated. The accreted terranes within the Tibetan Plateau experienced multiple stages of evolution. To track the geochemical characteristics of their associated lithospheric mantle through time, we can use mantle-derived magmas to constrain the mechanism of mantle enrichment. We report zircon U-Pb ages, major and trace element contents, and Sr-Nd isotopic compositions for Early Cretaceous and late Eocene mafic rocks in the southern Qiangtang terrane. The Early Cretaceous Baishagang basalts (107.3 Ma) are characterized by low K2O/Na2O (<1.0) ratios, arc-like trace element patterns, and uniform Sr-Nd isotopic compositions [(87Sr/86Sr)i = 0.7067−0.7073, εNd(t) = −0.4 to −0.2]. We suggest that the Baishagang basalts were derived from partial melting of enriched lithospheric mantle that was metasomatized by subducted Bangong−Nujiang oceanic material. We establish the geochemistry of the pre-collisional enriched lithospheric mantle under the southern Qiangtang terrane by combining our data with those from other Early Cretaceous mafic rocks in the region. The late Eocene (ca. 35 Ma) post-collisional rocks in the southern Qiangtang terrane have low K2O/Na2O (<1.0) ratios, and their major element, trace element, and Sr-Nd isotopic compositions [(87Sr/86Sr)i = 0.7042−0.7072, εNd(t) = −4.5 to +1.5] are similar to those of the Early Cretaceous mafic rocks. Based on the distribution, melting depths, and whole-rock geochemical compositions of the Early Cretaceous and late Eocene mafic rocks, we argue that the primitive late Eocene post-collisional rocks were derived from pre-collisional enriched lithospheric mantle, and the evolved samples were produced by assimilation and fractional crystallization of primary basaltic magma. Asthenosphere upwelling in response to the removal of lithospheric mantle induced the partial melting of enriched lithospheric mantle at ca. 35 Ma.

Duobagou Permian–Triassic granites from the Dunhuang orogenic belt, NW China: implications for the tectonic evolution of the southernmost Central Asian Orogenic Belt

2020 ◽  
pp. 1-17
Author(s):  
Zhendong Wang ◽  
Yuanyuan Zhang ◽  
Xiangjiang Yu ◽  
Zhaojie Guo
Keyword(s):  
Partial Melting ◽  
Tectonic Evolution ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Crustal Growth ◽  
Central Asian ◽  
Granitic Intrusions ◽  
Mantle Component ◽  
Type Granite ◽  
T Values

Abstract The Duobagou Permian–Triassic granites of the Dunhuang orogenic belt are of great importance in understanding the tectonic evolution of the southernmost Central Asian Orogenic Belt. LA-ICP-MS U–Pb zircon ages indicate that Permian–Triassic granitic intrusions from the Duobagou area formed at 276–274 Ma and 246 ± 1 Ma. These granites have high SiO2, Na2O and K2O, but low Al2O3, CaO and MgO contents and belong mainly to the high-K calc-alkaline I-type granite series. Based on whole-rock geochemistry and Sr–Nd and zircon Hf isotopes, the Duobagou Permian–Triassic granites were dominantly derived from the partial melting of lower continental crust formed during late Palaeoproterozoic to Mesoproterozoic times in a post-collisional extensional setting. Permian granites with zircon ϵHf(t) values of −5.4 to +3.1 and Hf model ages of TDM2 = 1.14–1.70 Ga indicate the involvement of a mantle component in their petrogenesis. Triassic granites with higher zircon ϵHf(t) values (+0.5 to +3.8) and TDM2 = 1.08–1.31 Ga suggest more juvenile sources caused by a greater contribution of mantle-derived melts, indicating a significant crustal growth. Regional extension from lithospheric delamination and heating from asthenospheric upwelling were proposed to have triggered the partial melting of lower crust, resulting in the generation of the Permian–Triassic magmatism. This may have been the mechanism for the significant crustal growth during Permian and Triassic times in the southernmost Central Asian Orogenic Belt.

scholarly journals Mineral Compositions of Syn-collisional Granitoids and their Implications for the Formation of Juvenile Continental Crust and Adakitic Magmatism

2020 ◽  
Vol 61 (3) ◽  
Author(s):  
Yuanyuan Xiao ◽  
Shuo Chen ◽  
Yaoling Niu ◽  
Xiaohong Wang ◽  
Qiqi Xue ◽  
...  
Keyword(s):  
Trace Element ◽  
Partial Melting ◽  
Continental Crust ◽  
Parental Magma ◽  
Age Dating ◽  
Trace Element Geochemistry ◽  
Crustal Growth ◽  
Tio2 Content ◽  
Mineral Phases ◽  
Mineral Compositions

Abstract Continentalcollision zones have been proposed as primary sites of net continental crustal growth. Therefore, studies on syn-collisional granitoids with mafic magmatic enclaves (MMEs) are essential for testing this hypothesis. The Baojishan (BJS) and Qumushan (QMS) syn-collisional plutons in the North Qilian Orogen (NQO) on the northern margin of the Tibetan Plateau have abundant MMEs in sharp contact with host granitoids, sharing similar constituent minerals but with higher modal abundances of mafic minerals in MMEs. The QMS host granitoids have high Sr/Y and La/Yb ratios, showing adakitic compositions, which are differentfrom the BJS granitoids. Based on bulk-rock compositions and zircon U-Pb age-dating, recent studies on these two plutons proposed that MMEs represent cumulates crystallized early from the same magmatic system as their host granitoids, and their parental melts are best understood as andesitic magmas produced by partial melting of the underthrusting upper ocean crust upon collision with some terrigenous sediments under amphibolite facies. Here, we focus on the trace-element geochemistry of the constituent mineral phases of both MMEs and their host granitoids of the QMS and BJS plutons. Weshow that different mineral phases preferentially host different trace elements; for example, most rare earth elements (REEs and Y) reside in titanite (only found in the QMS pluton), amphibole, apatite, epidote and zircon (mostly heavy-REEs); and high-field-strength elements (HFSEs) reside in biotite, titanite, amphibole and zircon. Based on the mineral chemical data, we show that for these two plutons, MMEs are of similar cumulate origin, crystallized from primitive andesitic melts in the early stage of granitoid magmatism. The primitive andesitic melts for these syn-collisional granitoids are most likely produced by the partial melting of the oceanic crust, supporting the hypothesis of continental crustal growth considering the syn-collisional granitoids represent juvenile continental crust. As evidenced by distinct mineral compositions, the two plutons have different parental magma compositions, for example higher TiO2 content and higher Sr/Y and La/Yb ratios in the QMS parental magmas, a signature best understood as being inherited from the source. The higher TiO2 content of the parental magma for the QMS pluton leads to the common presence of titanite in the QMS pluton (absent in the BJS pluton), crystallization of which in turn controls the trace-element (REE, Y, Nb, Ta and others) systematics in the residual melts towards an adakitic signature. Therefore, parental magmas with high TiO2 content and high Sr/Y and La/Yb ratios, as well as their further fractionation of titanite, are important factors in the development of adakitic compositions, as represented by the QMS host granitoids. This model offers a new perspective on the petrogenesis of adakitic rocks. The present study further demonstrates that, in general, mineral chemistry holds essential information for revealing the petrogenesis of granitoid rocks.

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