1:25万丁固幅、加措幅地质调查成果与进展

1:250 000 Dinggo and Gyamco Sheets in Xizang

关键词:  1:25万  地质调查  丁固幅  加措幅  成果与进展  西藏

Key words:  1:250 000  geological survey  Dinggo Sheet  Gyamco Sheet  development  Xizang

摘要:

地层方面,在冈玛错下石炭统日湾擦卡组上部灰岩中采获晚二叠世古生物化石组合;在查波错东岸中二叠统鲁谷组上部灰岩中采获中三叠世化石;在磨盘山一带侏罗系雁石坪组灰岩中采获、珊瑚化石,大部分应划分为二叠系;在他利克甘利山上三叠统肖茶卡组中采获早三叠世牙形刺,将其修订为下三叠统硬水泉组;在测区东北角新发现一套角度不整合于上三叠统肖茶卡组砂屑灰岩之上的火山岩;友谊沟南西侧前人所划石炭系木实热不卡群与前泥盆系之间的角度不整合接触关系不存在,二者实为同一套地层;在尖山至走构由茶错一带新发现一套中酸性火山岩及一套玄武岩;在峡峡定沟、麦尔则一带新发现一套安山岩;在则下龙一带新发现一套冲积成因的更新统砾岩;初步确定区内第四纪更新世有古大湖存在。岩石方面,原所划的昆楚克错岩体、加作巴热岩体、先遣岩体实为一个巨大岩基;在达尔应一带新发现一套富含云母的典型S型花岗岩;在冈玛日北西岗玛错断裂以北新发现一处花岗片麻岩;在达尔应一带新发现呈断夹块产出的石榴角闪中长片麻岩;在冈玛日一带发现呈岩片状产出的蓝片岩。构造方面,查明冈玛错断裂为一构造混杂岩带,区内存在上、中、下构造层次的变形。新发现一批铜、铁、金、石膏、玉石等矿点。

Abstract:

The Late Permian fossils are collected from the limestones in the upper part of the Lower Carboniferous Riwancaka Formation in the Gangmarco area; the Middle Triassic fossils from the Middle Permian Lugu Formation on the eastern bank of the Chabo Lake, and the fusulinid and coral fossils in the Mopanshan region from the Jurassic Yanshiping Formation, where the Jurassic strata should largely be defined as the Permian strata. The discovery of the Early Triassic conodonts from the Upper Triassic Xiaocaka Formation in the Talikeganlishan area permits the modification of the Formation into the Lower Triassic Yingshuiquan Formation. A succession of volcanic rocks is found to overlie unconformably the Upper Triassic Xiaocaka Formation calcarenite. There is no angular unconformity between the previously Carboniferous Mushirebuka Group on the southwestern side of the Youyi gully and the pre-Devonian strata, both of which should be assigned to the same succession of strata in nature. There occur intermediate and acidic volcanic rocks and basalts in the Jianshan-Zougouyouchaco zone; andesite in the Xiaxiadinggou-Merze zone, and alluvial Pleistocene conglomerates in the Zexialong region. It is inferred that the Pleistocene ancient lakes once appeared in this region. Lithologically, the previously Kunchukeco, Jiazuobare and Xianqian massifs should be incorported into a giant batholith. The new findings include mica-rich S-type granites and garnet amphibole andesine gneiss as faults or blocks in the Darying region; granite gneiss in the area north of the Gangmarco fault in northwestern Gangmari, and blueschist as slices in the Gangmari region. Tectonically, the Gangmarco fault is believed to be a tectonic mélange zone, where the structural deformation appears in the upper, middle and lower levels of structures. The copper, iron, gold, gypsum and jade ore spots are delineated in the surveyed areas.