1:250 000 Lhunze and Zara Sheets in Xizang

The establishment and improvement of the stratigraphic systems resulted in the division of the strata in the Lhunze and Zara Sheets into five stratigraphic subprovinces and thirty-five formal and informal stratigraphic units. The formerly Garbo Formation in the Dongkar region is redivided into three mappable units including the Qulonggongba Formation and the first and second members of the Lakang Formation. There is an unconformity between the Zongzhuo Formation and its underlying strata, and a parallel unconformity between the Jiabula Formation and Sangxiu Formation, Sangxiu Formation and Weimei Formation, Weimei Formation and Zhela Formation. Two SB 1 boundaries and two SB 2 boundaries are established. There occurs in the upper part of the Nyeru Formation a succession of gravelly medium-to coarse-grained lithic sandstone and grayish green silty slate with widespread ravinement surfaces. The newly sampled fossils include Conularia sichuanesis Gou et Yang and Conularia maantangensis et Yang in the Nyeru Formation. The Namgyaixoi Group consists dominantly of basic volcanic rocks in the slope-basin facies in which abundant thin-shelled bivalves occur. There also exist fault contacts among individual formation complexes and lithologic members in the Group. The plant fossils are recently collected in the Zhangcun Formation Complex. The ophiolitic mélanges are found in the strata between the Namgyaixoi Group and Nyeru Formation in the Yumai region on the northern flank of the Qungdogyang-Karreg-Yumai composite fault. The Nangxian mélanges in the Lhatog-Bailu zone consist of numerous tectonic slices. There is an isochron age of 625 Ma for the gneiss from the Namjagbarwa Group Complex near the Xiagele Bridge in Zara and a ⁴⁰Ar-³⁹Ar age of 921.17 Ma for the schist from the Rouqiecun Group Complex in Raorang. The volcanic strata contain seven volcanic horizons, and their tectonic settings are ascertained. An antimony-gold deposit is explored in the Mazhala region.