Petrogenesis and tectonic significance of the Late Permian–Middle Triassic calc-alkaline granites in the Balong region, eastern Kunlun Orogen, China

Abstract

Numerous calc-alkaline granitoid intrusions in the eastern Kunlun Orogen provide a valuable opportunity to constrain the evolution of the orogen. The age and genesis of these intrusions, however, remain poorly understood. The granitoid intrusions near the Balong region, eastern Kunlun Orogen, consist of granodiorite, diorite and syenogranite. The granodiorite contains crystallized segregations, abundant mafic microgranular enclaves (MMEs) and small quartz diorite stocks. In situ zircon U–Pb dating reveals that the granodiorites and quartz diorites were emplaced between 263 and 241 Ma, whereas the syenogranite was produced at c. 231 Ma. The granodiorite and quartz diorite have a calc-alkaline affinity and are metaluminous and Na-rich, with slightly enriched Sr–Nd isotope compositions. The granodiorite is characterized by fractionated REE patterns, whereas the quartz diorite displays a relatively flat REE pattern. The MMEs are consistent with the granodiorite in terms of incompatible elements and Sr–Nd isotope composition. Compared to the granodiorite and diorite, the syenogranite has higher SiO2, K, Rb, Th and Sr contents and a lower Rb/Sr ratio. The results presented here, when combined with regional geological data, indicate that the granodiorite and quartz diorite were derived from dehydration melting of mafic lower crustal rocks during the N-directed subduction of the Anyemaqen ocean lithosphere in Late Permian–Middle Triassic times, whereas the syenogranite was produced at a higher crustal level in a syn-collisional setting compared to the granodiorite.

40Ar–39Ar age and geochemistry of subduction-related mafic dikes in northern Tibet, China: petrogenesis and tectonic implications

“…Xiong et al 2011). Previous studies of precise zircon U-Pb analyses in the EKOB suggest that the ages of granitoid intrusions and volcanics range from 263 to 213 Ma Ding et al 2011;Xiong et al 2012;Zhang et al 2012). The ages of the Buqingshan and Dur'ngoi ophiolite (the remnants of the A'nymaqen Palaeo-Tethyan oceanic lithosphere) range from 345 to 308 Ma (Chen et al 2001;Yang et al 2009;Liu et al 2011).…”

“…Email: cqma@cug.edu.cn A'nyemaqen Palaeo-Tethyan Ocean and the subsequent continent-continent collision ( Figure 1B; e.g. Yang et al 2005;Luo et al 2008;Xiong et al 2011Xiong et al , 2012Zhang et al 2012). Many studies have been undertaken on the granitoid intrusions and volcanic rocks in the EKOB, but few have focused on the petrogenesis and tectonic settings of the mafic dike swarms (e.g.…”

Petrogenesis and tectonic implications of Triassic mafic complexes with MORB/OIB affinities from the western Garzê-Litang ophiolitic mélange, central Tibetan Plateau

“…The basaltic rocks of the ophiolites are composed of normal (N)-MORB, enriched (E)-MORB and minor OIB affinities (Bian et al, 2004;Guo et al, 2007;Yang et al, 2009) and their ages range from 345 Ma to 308 Ma (Chen et al, 2001;Yang et al, 2009). In the EKL, Early Permian to Late Triassic (278-213 Ma) magmatic rocks, including granites, mafic dykes and volcanic rocks, are widespread because of the subduction of the A'nyemaqen-Kunlun Ocean and subsequent continental collision Xiong et al, 2014;Zhang et al, 2012a). The JS is distributed along the Jinsha River separating the North Qiangtang (NQ)-Changdu (CD)-Simao (SM) terrane to the south or west from the BSG -Yidun Arc (YA) terrane to the north and east.…”

Petrogenesis and geodynamic implications of the Mid-Triassic lavas from East Kunlun, northern Tibetan Plateau

“…In addition, sample HSG1-1 has a Nb/Ta ratios of 14.2, which is inconsistent with the Nb/Ta ratio of 11-12 for magma solely derived from the melting of crustal material (Green, 1995;Li et al, 2015a). For the voluminous coeval intrusive conterparts in the EKOB, the widespread occurrence of mafic microgranular enclaves in granitoids is recognized as a line of evidence for magma mixing (e.g., Li et al, 2012a;Zhang et al, 2012;Xiong et al, 2012Xiong et al, , 2014. This implies a regional extension that results in the underplating of mantle-derived magma onto the base of continental crust beneath the EKOB (e.g., Zhang et al, 2012;Xiong et al, 2014).…”

“…For the voluminous coeval intrusive conterparts in the EKOB, the widespread occurrence of mafic microgranular enclaves in granitoids is recognized as a line of evidence for magma mixing (e.g., Li et al, 2012a;Zhang et al, 2012;Xiong et al, 2012Xiong et al, , 2014. This implies a regional extension that results in the underplating of mantle-derived magma onto the base of continental crust beneath the EKOB (e.g., Zhang et al, 2012;Xiong et al, 2014). Therefore, we argue that the HSG volcanic rocks in the EKOB were derived from partial melting of both the mafic lower crust and the underlying lithospheric mantle (e.g., Li et al,…”