Petrogenesis of the Triassic Dongjiangkou pluton in the South Qinling orogenic belt, Central China: Insufficient magma mixing of mafic and felsic magmas

Compositional Diversity of Early Mesozoic Granites in South Qinling: Derivation from Heterogenous Basement Rocks in the Orogenic Belt

“…They are exposed as large plutons usually in the terrain, constituting intermediate to felsic rocks in composition, and are often emplaced in different time or magmatic stages, ranging from ~250 Ma to ~180 Ma [20][21][22][23][24]. Representatives of these are the Miba, Guangtoushan, Wulong, and Dongjiangkou plutons in the east of the Hui-Cheng basin [6,25,26] and the Baoji and Mishuling plutons in the north of the basin [5,27]. Several plutons contain numerous mafic microgranular enclaves, such as the Miba, Dongjiangkou, and Mishuling plutons [5,6], and have geochemical characteristics of I-type granite, while some large plutons, e.g., the Guangtoushan and Baijiazhuang plutons, have an S-type affinity in geochemical composition and mineral assemblage [4,26].…”

“…Representatives of these are the Miba, Guangtoushan, Wulong, and Dongjiangkou plutons in the east of the Hui-Cheng basin [6,25,26] and the Baoji and Mishuling plutons in the north of the basin [5,27]. Several plutons contain numerous mafic microgranular enclaves, such as the Miba, Dongjiangkou, and Mishuling plutons [5,6], and have geochemical characteristics of I-type granite, while some large plutons, e.g., the Guangtoushan and Baijiazhuang plutons, have an S-type affinity in geochemical composition and mineral assemblage [4,26]. These Triassic rocks in South Qinling have wide variations in geochemical composition and mineral assemblage, implying diversely magmatic origins, such as the Miba, Guangtoushan, Mishuling, and Wulong plutons [4][5][6]26,27].…”

“…Several plutons contain numerous mafic microgranular enclaves, such as the Miba, Dongjiangkou, and Mishuling plutons [5,6], and have geochemical characteristics of I-type granite, while some large plutons, e.g., the Guangtoushan and Baijiazhuang plutons, have an S-type affinity in geochemical composition and mineral assemblage [4,26]. These Triassic rocks in South Qinling have wide variations in geochemical composition and mineral assemblage, implying diversely magmatic origins, such as the Miba, Guangtoushan, Mishuling, and Wulong plutons [4][5][6]26,27]. These granitic rocks were magmatic products derived from diversely tectonic settings, commonly interpreted as subduction-related [28], early subduction-related to late continental collision [12,24,27,29,30], or syn-to post-collisional settings [31] in the literature.…”

“…These geochemical features were proposed as evidence for an origin of partial melting of the subducted oceanic crust and sedimentary material in an arc setting [31,46]. The Wulong and Dongjiangkou plutons in the east of the Hui-Cheng basin are composed of dioritic and granitic rocks forming at ~220-210 Ma and have been interpreted as magmatic products in the post-collisional setting [6,22]. The ~242 Ma Xihe and ~214 Ma Baijiazhuang plutons exposed in the west of the basin, mainly consisting of peraluminous granite, yield S-type affinity in geochemical composition and mineral assemblage and were interpreted to be derived from pelitic source [4].…”

“…Based on several previous studies, numerous large granitoid plutons of Early Mesozoic age are exposed in the South Qinling terrain; they consist of complex rock types and were formed in different tectonic settings in the late orogenic stages that resulted from the final collision between the South and North China blocks. They are characterized by compositional variances in elemental and isotopic compositions [4][5][6], but the origin of this compositional diversity still needs to be further comprehended. In the present study, the Guangtoushan and Miba granitoid plutons, exposed adjacent to the Hui-Cheng basin, were selected as concrete objects.…”