Potassic/ultrapotassic intrusions at the southwestern margin of the Yangtze Craton, southwestern China: Petrogenesis and implications for the metal and fluid source of non-arc porphyry Cu–(Mo–Au) deposits

Pre-Late Eocene position of the Lüchun-Jinping microblock in western Yangtze Craton: Constraints from Eocene-Oligocene lamprophyres in southeastern Tibet

“…Therefore, the lamprophyres from the Chang'an (CA14-116-1), Laowangzhai (LWZ1701-1) and Daping (DP17-1a) districts were emplaced at 34.7 ± 0.4 Ma, 34.6 ± 0.3 Ma, and 33.3 ± 0.3 Ma, respectively. These are consistent with the results of previous studies by different dating methods of the potassic-ultrapotassic mafic rocks in the Ailaoshan tectonic belt and western Yangtze Craton (Guo et al, 2005;Lu et al, 2015;Shen et al, 2021;Wang et al, 2001), as summarized in Table S1, and are similar to the adjacent intermediate-felsic intrusions along the Jinshajiang-Ailaoshan magma belt (37-32 Ma, Lu et al, 2012;Xu et al, 2012;Xin et al, 2020). Therefore, the lamprophyres from the Lüchun-Jinping microblock are the products of Eocene-Oligocene magmatism, possibly related to post-collisional transpressional and extensional tectonic settings at 42 to 26 Ma, following the India-Asia continental collision (Hou et al, 2007).…”

“…The new zircon U -Pb ages (34.7-33.3 Ma, Fig. 3), combined with published data (Wang et al, 2001;Xin et al, 2020;Zhu et al, 2013), imply that almost all potassic-ultrapotassic lamprophyres and potassic felsic intrusions in the Ailaoshan tectonic belt formed prior to ductile shearing, precluding a genetic relationship between sinistral shearing and potassic magmatism. In addition, the Eocene-Oligocene potassic magmas are not restricted to the Ailaoshan-Red River magmatic belt, but also occur between Yongping-Jianchuan proximal to the Ailaoshan-Red River shear zone, and Xichang in western Sichuan, which is ~270 km east of the shear zone (Guo et al, 2005;Lu et al, 2012), The Eocene-Oligocene potassic magmas were, therefore, widely developed in southeastern Tibet covering ~90,000 km 2 zone across the Simao Block and the Yangtze Craton (Fig.…”

“…1c). The felsic intrusions consist of syenite, granite, and quartz monzonite with zircon U-Pb ages ranging between 36.3 and 33.7 Ma (Xin et al, 2020;Xu et al, 2012;Zhu et al, 2013). The widely exposed mafic units are dominated by lamprophyre dykes, with minor mafic lavas.…”

Implications of Nd isotopic mapping for crustal composition and metallogenesis in the Sanjiang orogenic belt (SW China)

“…In the southeasternmost part of the EQST, the highest ε Nd (t) values correspond to the Ailaoshan Suture and the Yaxuanqiao Arc, and the samples used in this study can be divided into two groups by formation age: ~230 Ma (Liu et al, 2014) and ~35 Ma (Xin et al, 2020). The former does not contain coeval or earlier mafic-intermediate rocks, which indicates that these granites originated from a basic lower crust (Liu et al, 2014).…”

Petrogenesis and tectonic significance of Neoarchean (~2.6 Ga) alkaline ultrapotassic granitic gneisses from the southeastern margin of the North China Craton: Constraints from U-Pb dating, Hf isotope and petrogeochemistry

“…Ultrapotassic rocks have been described worldwide, particularly in post-collisional settings. Post-collisional potassic to ultrapotassic magmatism has been recognized in Tibet, Italian peninsula, and Yangtze Craton (Conticelli et al, 2002;Miller et al, 1999;Turner et al, 1996;Williams et al, 2004;Xin et al, 2020). Although geographically widespread, these rock suites are volumetrically and temporally limited.…”