The Triassic granitoids are widely exposed along the Changning‐Menglian suture zone (CMSZ) in SW China, which are the products of Palaeo‐Tethyan closure and are characterized by highly variable geochemical compositions. However, details of the implied source heterogeneity and magma genesis have not been well constrained. In this study, we present zircon U–Pb isotopes and trace elements, whole‐rock major and trace element compositions and Sr–Nd isotopes of Triassic granitoids from the giant Yunling and Lincang plutons developed in the CMSZ. Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating indicates that they were emplaced at ca. 227–216 Ma. Geochemically, these Triassic granitoids can be classified into three types. The Yunling low‐silica granodiorites (Type 1) are characterized by the presence of amphibole‐bearing mineral assemblages, high TiO 2 and FeO T + MgO, belonging to I‐type granite and calc‐alkaline series. The Lincang low‐silica granodiorites (Type 2) are metaluminous to peraluminous with the occurrence of amphibole, consistent with transitional I‐S‐type granites. Compared to Type 1 and 2, the Lincang high‐silica (SiO 2 > 70%) alkali feldspar granites and syenogranites (Type 3) display lower CaO, TiO 2 , P 2 O 5 , MgO + FeO T , Eu, Sr, and Zr contents, belonging to fractionated‐type granites. Three types of granitoids collectively show enriched Rb, Th, K, and Pb, depleted Ba, Sr, Ti, and Eu, negative whole‐rock ε Nd ( t ) (−11.0 to −10.7) and old T DM2 ages of 1,886–1,855 Ma, indicating the affinity of middle‐upper crustal derivation. New zircon U–Pb dating yields an age range of 2,391–322 Ma for inherited zircons with two clusters at ca. 460 and 956 Ma, suggesting that their crustal source might be the basement of the Simao Block rather than the basement of the Proterozoic Lancang Group. Diverse geochemical compositions indicate that the parental magma of the Triassic granitoids in the CMSZ originated from the partial melting of a heterogeneous source, and experienced magma mixing, assimilation with Lancang Group meta‐sandstone and fractional crystallization. Considering the exhumation of the high‐pressure metamorphic rocks in the CMSZ at Triassic, the upwelling of the asthenosphere after the Palaeo‐Tethyan closure increased the geothermal gradient of the lithosphere and triggered extensive crust melting in a post‐collisional setting.
Being the largest marginal sea in the western Pacific Ocean, South China Sea (SCS) has been brought into focus since 1970s due to the prolific biological resources and fossil energy preserved in the deep-sea area, particularly tectonic-controlled structures that determine basin sedimentation and hydrocarbon accumulation. Understanding the origin and tectonic evolution of SCS is necessary to better constrain the location of various resources. In this paper, we synthesize mainstream perspectives on the SCS sea floor spreading, including pulling apart of SCS driven by plate strike-slip during Eocene-Miocene, opening up of the Proto-SCS in late Oligocene-Miocene by subduction beneath NW Borneo along the margin and further spreading during Late Oligocene-mid Miocene due to lithospheric mantle flow upwelling. Existing tectonic evolution models of SCS are reviewed and their controversies are discussed. An intergraded model is proposed to provide a comprehensive consideration on the interpretation of the SCS formation and development.
<p>Supplemental file 1: Calculation details of nonmodal batch melting modeling of peridotite with different proportions of garnet in Figure 6B. Supplemental file 2: Calculation details of mixing model of melt derived from garnet peridotite and decarbonated eclogite in Figure 11.</p>
Calculation details of non-modal batch melting modeling of peridotite with different proportions of garnet in Fig. 7b and mixing model of melt derived from garnet peridotite and carbonated eclogite in Fig. 10.
Calculation details of non-modal batch melting modeling of peridotite with different proportions of garnet in Fig. 7b and mixing model of melt derived from garnet peridotite and carbonated eclogite in Fig. 10.
These materials are table 1, table 2 and supplementary file of the manuscript entitled of "Factors controlling Sc partitioning between clinopyroxene and magma: Insights from first-principles calculations".
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