1:25万土则岗日幅、托和平错幅地质调查成果与进展

1:250 000 Toza Kangri and Tuohepingco Sheets in Xizang

关键词:  1:25万  地质调查  土则岗日幅  托和平错幅  成果与进展  西藏

Key words:  1:250 000  geological survey  Toza Kangri Sheet  Tuohepingco Sheet  development  Xizang

摘要:

地层古生物方面,(1)建立和重新厘定了8个群级、24个组级及多个非正式(岩石)地层单位和填图单位;(2)在雅西尔沟一带,将泥盆系厘定为兽形湖组和拉竹龙组;(3)万泉河北部一带的原泥盆系雅西尔群,依据化石成果被重新厘定为下三叠统,并新建万泉河群;(4)发现下白垩统铁隆滩群与上侏罗统松木西错群等角度不整合接触关系;(5)新近系康托组角度不整合于下伏地层之上,在康托组一、二段间发现角度不整合接触关系;(6)初步将羌塘地层区原划分的前泥盆系阿木岗群改为石炭—二叠系;(7)初步查明了霍尔巴错群岩石组合等基本特征;(8)进一步确定了区内三叠系肖茶卡群与下伏地层间的角度不整合接触关系;(9)在三岛湖侏罗系实测地层剖面上采集了大量古生物化石。岩石方面:(1)在托和平错一带新填绘出大量基性岩墙和酸性岩株(脉);(2)初步认为展金组火山岩形成于洋岛环境,时代为早二叠世;(3)否定了托和平错一带分布有新生代火山岩出露的结论;(4)新发现了甜水湖北新生代碱性火山岩,初步确定其时代较鱼鳞山火山岩新。构造上,确定了窝尔巴错-拜惹布错断裂带为喀喇昆仑地块和羌塘地块的分界断裂,基本查明了断裂带特征及构造属性。矿产方面,新发现一处大型砂金矿。

Abstract:

The recent advances in the geological survey of the 1:250 000 Toza Kangri and Tuohepingco Sheets in Xizang are generalized as follows. (1) Eight group-scale, twenty-four formation-scale and several informal (litho)stratigraphic units and mappable units are designated or redelimited. (2) The Devonian strata in the Yaxi'ergou region are assigned to the Shouxinghu and Lazhuglung Formations. (3) The formerly Devonian Yaxi'er Group in the northern part of the Wanquan River are redivided and incorporated into the Lower Triassic strata Wanquanhe Group in the light of fossil data available. (4) There is an angular unconformable contact between the Lower Cretaceous Tielongtan Group and the Upper Jurassic Sumxico Group. (5) The Neogene Kangtog Formation lies with an angular unconformity upon the underlying strata, and there exists an angular unconformable contact between the first and second members of the Kangtog Formation. (6) The formerly pre-Devonian Amugang Group is redivided into the Carboniferous-Permian strata in the Qingtang region. (7) The main characteristics of the Horbaco Group rocks are ascertained. (8) The Triassic Xiaocaka Group is confirmed to be overlain with an angular unconformity upon the underlying strata. (9) abundant fossils are collected from the Sandaohu Jurassic measured stratigraphic section. The recent progress in petrology includes:(1) the mapping of abundant basic dikes and acidic stocks (veins) in the Tuohepingco region; (2) knowledge of the oceanic-island environment for the formation of the Zhanjin Formation volcanic rocks during the Early Permian; (3) absence of the Cenozoic volcanic rocks in the Tuohepingco region, and (4) discovery of the Cenozoic alkaline volcanic rocks in the area north of the Tianhui Lake with a younger age than that of the Yulinshan volcanic rocks. Tectonically, the Orbaco-Bairabco fault is interpreted as a boundary fault between the Karakorum landmass and Qiangtang landmass. In addition, a large-sized placer gold deposit is explored as well.