⁴⁰ Ar/ ³⁹ Ar Dating of Detrital White Mica as a Complementary Tool for Provenance Analysis: A Case Study from the Cenozoic Qaidam Basin (China)

Abstract

When classic petrographic analysis of the modal composition of sandstones yields no distinction between different source regions, 40 Ar/ 39 Ar dating of detrital white mica can provide vital information on the age of a source area and thus link the sediments to a specific provenance in the hinterland. This approach is exemplified by a case study of the intramontane Qaidam Basin (western China). While the geology of the surrounding mountains of the Qaidam Basin shows considerable lithological variation and the basin's palaeoclimate changed from semi-arid to arid, modal analysis of sandstones from two sections in the northwestern basin, as well as a section on the eastern margin, yielded no significant spatial or temporal differences. All sandstones, most of them classified as lithic wackes with matrix/cement contents between 14 and 39%, plot mainly in the recycled orogenic field of Dickinson's ternary discrimination diagrams for a tectonic environment. The sandstones are quartz dominated, with quartz contents of 33-65% and relative high contents of feldspar and lithic grains. On the other hand, 40 Ar/ 39 Ar total-fusion age data obtained from detrital white mica of between 123 and 546 Ma yielded three age clusters (120-180, 220-280, 350-450 Ma) that could be assigned to certain provenance areas within the early Palaeozoic and Permian basement in the Altyn and Qimantagh mountains. This contrasts with the Lulehe section in the east of the basin, where exclusively Permian ages between 250 and 279 Ma were found. This significant difference in age distribution, and thus provenance, could not be deduced from sandstone composition. The results of this study show how 40 Ar/ 39 Ar thermochronology can complement classic point-count analysis.

Petrogenesis of the Carboniferous Ghaleh-Dezh metagranite, Sanandaj–Sirjan zone, Iran: constraints from new zircon U–Pb and40Ar/39Ar ages and Sr–Nd isotopes

“…The 40 Ar/ 39 Ar analytical techniques follow those described by Handler et al (2004) and Rieser et al (2006). To obtain 40 Ar/ 39 Ar analyses, a sample of mylonitic granite (sample N1-2) was crushed, sieved, washed with deionized water and oven-dried.…”

Mesozoic-Cenozoic evolution of the Eastern Kunlun Range, central Tibet, and implications for basin evolution during the Indo-Asian collision

“…Age assignments for Cenozoic strata in the Qaidam basin come from biostratigraphy, magnetostratigraphy, fission track, and 40 Ar/ 39 Ar dating of detritus in exposed strata. These data are subsequently correlated across the basin using a dense network of seismic reflection profiles and drill hole data (e.g., Yang et al, 1992;Xia et al, 2001;Sun et al, 2005;Rieser et al, 2006aRieser et al, , 2006bFang et al, 2007;Yin et al, 2008b;Lu and Xiong, 2009;Chen et al, 2011;McRivette et al, 2019;Ke et al, 2013;Yu et al, 2014;Cheng et al, 2016;Bush et al, 2016;Ji et al, 2017;A. Chen et al, 2017a;Wang et al, 2017).…”

“…Chen et al, 2017a;Wang et al, 2017). Cenozoic stratigraphic division and age assignments from oldest to youngest units are as follows (Chen et al, 2010): Paleocene to lower Eocene Lulehe Formation (Yang et al, 1992;Rieser et al, 2006a;Ke et al, 2013;Yu et al, 2014;Ji et al, 2017), middle Eocene to lower Oligocene Xiaganchaigou Formation (Yang et al, 1992;Sun et al, 2005;Yu et al, 2014;Li et al, 2016;Ji et al, 2017), upper Oligocene Shangganchaigou Formation (Sun et al, 1999;Yu et al, 2014;Li et al, 2016;Chang et al, 2015;Ji et al, 2017), lower to middle Miocene Xiayoushashan Formation (Sun et al, 1999;Chang et al, 2015;Ji et al, 2017;Li et al, 2016), middle to upper Miocene Shangyoushashan Formation (Sun et al, 1999;Wang et al, 2007;Fang et al, 2007;Chang et al, 2015;Li et al, 2016;Ji et al, 2017), and upper Miocene and Pliocene Shizigou Formation (Sun et al, 1999;Fang et al, 2007;Wang et al, 2007;Yu et al, 2014;. The total thickness of Cenozoic Qaidam deposits exceeds 16 km in the west and progressively thins eastward to less than 2 km in the east (Yin et al, 2008b;Chen et al, 2010).…”

Cenozoic tectonic evolution of the Qaidam basin and its surrounding regions (Part 3): Structural geology, sedimentation, and regional tectonic reconstruction

“…The Qaidam basin preserves a complete record of Cenozoic sedimentation and has been the focus of numerous sedimentological and stratigraphic studies (Bally et al, 1986;Wang and Coward, 1990;Song and Wang, 1993;Huang et al, 1996;Zhang, 1997;Métivier et al, 1998;Xia et al, 2001;Yin et al, 2002;Sobel et al, 2003;Sun et al, 2005;Rieser et al, 2005Rieser et al, , 2006aRieser et al, , 2006bZhou et al, 2006). For example, Cenozoic basin history has been established by analyzing thickness distribution (Huang et al, 1996), paleocurrent analysis (Hanson, 1998), lithofacies patterns (e.g., Zhang, 1997), sandstone petrology (Rieser et al, 2005), and 40 Ar/ 39 Ar detrital-mica ages (Rieser et al, 2006a(Rieser et al, , 2006b). In addition, Cenozoic chronostratigraphy of the basin has been investigated in detail by using fossils (i.e., spores, ostracods, and pollen), basin-wide seismic stratigraphic correlation, magnetostratigraphic studies, and fi ssion-track dating of detrital grains (Huo, 1990;Qinghai Bureau of Geology and Mineral Resources, 1991;Yang et al, 1992Yang et al, , 1997Yang et al, , 2000Song and Wang, 1993;Huang et al, 1996;Xia et al, 2001;Nansheng, 2002;Sun et al, 1999Sun et al, , 2005.…”