1:25万隆子县幅、扎日区幅地质调查成果与进展

1:250 000 Lhunze and Zara Sheets in Xizang

关键词:  1:25万  地质调查  隆子县幅  扎日区幅  成果与进展  西藏

Key words:  1:250 000  geological survey  Lhunze Sheet  Zara Sheet  development  Xizang

摘要:

建立和完善了测区地层系统,将地层划为5个地层分区,并划分出35个正式、非正式地层单位;将洞嘎曲一带原划的嘎波组划分为曲龙共巴组及拉康组一、二段3个填图单元;确认宗卓组与下伏地层为角度不整合,甲不拉组与桑秀组、桑秀组与维美组、维美组与遮拉组之间均为平行不整合接触;确立了2个SB₁界面和2个SB₂界面;首次发现涅如组上部发育一套含砾中粗粒岩屑砂岩及灰绿色粉砂质板岩,并广泛发育冲刷面,并在该组中新采获四川方锥石和马鞍塘方锥石化石;朗杰学群中含大量基性火山岩,总体上为斜坡-盆地相,产大量薄壳型双壳,各岩组、岩性段间多呈断层接触;在章村岩组中新采获植物化石。在邛多江-卡拉-玉门复合断裂北侧的玉门一带朗杰学岩群与涅如组间新发现蛇绿混杂岩,基质中采获化石;发现拉多—白露一带朗县混杂岩由众多的构造岩片组成。在扎日区的夏格勒桥附近的南迦巴瓦岩群片麻岩和绕让肉切村岩群片岩中新的同位素年龄。查明区内含火山岩的地层有7个层位;查明了火山岩的形成的构造环境。在马扎拉一带发现了锑金矿。

Abstract:

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.