藏北羌塘南部走构由茶错地区火山岩定年与康托组时代的厘定  

Age dating of the Zougouyouchacuo volcanic rocks and age determination of the Kangtog Formation in southern Qiangtang, northern Tibet, China.

作　　者：李才[1] 黄小鹏[1] 牟世勇 迟效国[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]贵州省地质调查研究院,贵州贵阳550005

出　　处：《地质通报》2006年第1期226-228,共3页Geological Bulletin of China

基　　金：中国地质调查局<青藏高原地层格架建立与完善>项目(200313000054);<1:25万玛依岗日幅区域地质调查>项目(200313000015)部分成果。

摘　　要：康托组在羌塘南部地区分布广泛,是青藏高原始新世大规模隆升以后首先接受的陆相碎屑和火山沉积,以往根据时代跨度较大的生物化石将其时代确定为中新世,但一直存在争议。羌南走构由茶错康托组中呈层状出露的火山岩面积约120km2,主要岩性为玄武质粗面安山岩,保存有完好的火山口和火山颈。40Ar-39Ar积分年龄为30.5Ma±0.6Ma,K-Ar法年龄为33.3Ma±0.5Ma、29.3Ma±0.4Ma、32.3Ma±0.5Ma、28.4Ma±0.4Ma,为渐新世早期。结合区域上康托组与伴生火山岩的相互关系,确定走构由茶错、康托、鱼鳞山和纳丁错等地的火山岩是康托组的组成部分。根据走构由茶错火山岩同位素定年结果将康托组的时代由中新世厘定为渐新世,羌塘地区大规模隆升以后接受沉积的时间前推了大约10Ma。The Kangtog Formation, which are widespread in southern Qiangtang, is the first continental clastic and volcanic sediments following the Eocene extensive uplift of the Qinghai-Tibet Plateau. Previously, according to the fossils with a wide time span, the Kangtog Formation was determined to be Miocene. However, this conclusion has long been controversial. The layered volcanic rocks in the Kangtog Formation at Zougouyouchacuo, southern Qiangtang, cover an area of -120 km^2 and are mainly composed of basaltic trachyandesite, with crates and necks well preserved. The rocks have a 40^Ar-39^Ar age of 30.5± 0.6 Ma and K-Ar ages of 33.3±0.5, 29.3±0.4, 32.3±0.5 and 28.4±0.4 Ma, suggesting an early Oligocene age. According to the age data, combined with the regional relationships between the Kangtog Formation and its associated volcanic rocks, it may be concluded that the volcanic rocks at Zougouyouchacuo, Kangtog, Yulinshan and Nadingcuo are a component part of the Kangtog Formation. According to the isotopic dating of the Zougouyouchacuo volcanic rocks, it is suggested that the Kangtog Formation should be determined to be Miocene in age rather than Oligocene. This age advances the time of deposition in the Qiangtang area after its large-scale uplift for -10 Ma.

关 键 词：西藏羌南地区 走构由茶错 康托组 同位素年代学 渐新世 

分 类 号：P588.144[天文地球—岩石学] P534.614[天文地球—地质学]