Relict Proterozoic basement in the Nanling Mountains (SE China) and its tectonothermal overprinting

Abstract

The basement beneath the Caledonian belt in SE China has been overprinted by Indosinian and Yanshanian events and is poorly known. In situ U‐Pb and Hf‐isotope analysis of zircons from granites and surrounding rocks in the Nanling Mountains area of the fold belt reveal that the Lanhe felsic gneiss is an outcrop of Mesoproterozoic basement, probably with a partly Late Archean protolith. This is consistent with Nd model ages of granites in this region, and exposures of Cathaysia basement in the coastal area of SE China. In the Nanling Mountains, this basement was reactivated to generate granitoid rocks during the Caledonian, Indosinian, and Yanshanian tectonothermal events. The Caledonian overprint is documented in extensive exposures of the Zhuguang migmatites (425–470 Ma) and by previous U‐Pb zircon dating of adjacent granites. The Jiangnan granite may be of similar age, but strongly reworked. The Indosinian overprint resulted in the formation of granites such as the Luxi and Xiazhuang bodies (233–246 Ma) in the Guidong complex. The Yanshanian overprint produced the most widely distributed granites (circa 160 Ma) such as the Jiufeng and Fogang bodies, and parts of the Guidong complex. Hf‐isotope data show that all of the Phanerozoic magmatic rocks were derived from the Mesoproterozoic basement (and minor Archean components), without obvious contributions from juvenile sources. The presence of zircons with Archean age (2.5–2.7 Ga) in both the Lanhe gneiss and Devonian sediments indicates that the Badu and Mayuan groups may not be the oldest basement of the Cathaysia block. Some Archean basement (circa 2.5–2.7 Ga) may still be exposed but unrecognized in this region, and Cathaysia may include Archean microcontinental fragments.

Kwangsian and Indosinian reworking of the eastern South China Block: Constraints on zircon U–Pb geochronology and metamorphism of amphibolites and granulites

“…The metavolcanic samples of the Wanquan and Mamianshan Groups gave the SHRIMP zircon U-Pb ages of 728-826 Ma (Li WX et al, 2005;Wan et al, 2007;Li ZX et al, 2010). Amphibolite interlayers in the Chencai Group are dated at 832±23 Ma (in this study) Li, 1997;Xiang et al, 2008;Yu et al, 2009;Li XH et al, 1998;Li LM et al, 2011 ;Xu et al, 2005;Yu et al, 2006Yu et al, , 2007Yu et al, , 2009Yu et al, , 2010Wan et al, 2007Wan et al, , 2010Li ZX et al, 2010;Wang et al, , 2011Li WX et al, 2005 ;Li WX et al, 2005;Charvet et al, 2010; this study…”

“…U-Pb analyses for five samples were carried out at the Institute of Geology and Geophysics, the CAS, using a Laser ICP-MS connected to a 193 nm excimer laser ablation system. The instrumental setting and detailed analytical procedure have been described by Wu et al (2006) (Li, 1997) and detrital zircons of 3.6-2.5 Ga (Xu et al, 2005;Yu et al, 2006) that was strongly reworked at ca. 446-425 Ma (e.g., Wan et al, 2007;Charvet et al, 2010;Wang et al, 2011).…”

Detrital zircon U-Pb geochronology and Lu-Hf isotopic compositions of the Wuliangshan metasediment rocks in SW Yunnan (China) and its provenance implications

“…Figure 7. Frequency pattern of detrital zircon U-Pb ages for the sedimentary rocks from the Cathaysia (data are from Li et al, 2012;Yu et al, 2010;Wan et al, 2010Wan et al, , 2007Wang G S et al, 2009;Wang Y J et al, 2007;Yan et al, 2006;Xu et al, 2005) and Yangtze Block (data are from Duan et al, 2011;Yan et al, 2011;Li R B et al, 2010;Li X H et al, 2009Li X H et al, , 2008She, 2007;Zhang et al, 2006;Zheng et al, 2006), Tethyan-Himalaya (data are from Li et al, 2015;Usuki et al, 2013;Wang et al, 2013;Dong et al, 2011;Zhu et al, 2011;Myrow et al, 2010;McQuarrie et al, 2008;Gehrels et al, 2003) and Ailaoshan tectonic zone (data are from Nie, 2015 andWang et al, 2014), along with Wuliangshan Group (this study).…”

“…In order to better evaluate the provenance of the Wuliangshan Group, it is statistically synthesized for the reported detrital zircon U-Pb ages for Late Paleozoic sedimentary rocks from the Yangtze, Cathaysia Block and the Ailaoshan and Tethys-Himalayan tectonic zones (Li D P et al, 2015;Nie, 2015;Wang Q F et al, 2014;Usuki et al, 2013;Wang Y J et al, 2013Wang Y J et al, , 2007Li X H et al, 2012Li X H et al, , 2009Li X H et al, , 2008Dong et al, 2011;Duan et al, 2011;Yan Y et al, 2011;Zhu et al, 2011;Li R B et al, 2010;Myrow et al, 2010;Yu et al, 2010;Wan et al, 2010Wan et al, , 2007Wang G S et al, 2009;McQuarrie et al, 2008;She, 2007;Yan D P et al, 2006;Zhang et al, 2006;Zheng et al, 2006;Xu et al, 2005;Gehrels et al, 2003), as shown in Fig. 7.…”

Geochronology, petrogenesis and metallogeny of Piaotang granitoids in the tungsten deposit region of South China

“…With respect to the Precambrian metamorphic basement rocks distributed in western Cathaysia, such as Longchuan gneiss in northeast of Guangdong, Lanhe gneiss and Tanxi gneiss in northern Guangdong, Zengcheng gneiss in central Guangdong, and Xunwu gneiss in southern Jiangxi, their protoliths are all Neoproterozoic sedimentary rocks (Xu et al, 2005;Yu et al, 2006Yu et al, , 2007. As for the granulitefacies metamorphic rocks distributed in southwestern Fujian Province and the Yunkai areas which may represent lower crustal component are all parametamorphites, their protoliths are also Neoproterozoic sedimentary rocks (Yu et al, 2006).…”