摘要
在塔里木盆地南缘和田地区的阿其克、皮牙曼、杜瓦、康开依、桑株水库一带断续出露一套浅变质岩地层,主要岩石类型有变质杂砂岩、变质钙质砂岩、细粒片岩及少量千枚岩、变质砾岩、大理岩等.岩石中主要变质矿物为绿泥石、白云母、石英、方解石和少量黑云母、钠长石.本文着重就岩石中片状变质矿物绿泥石、白云母、黑云母的发育特点、化学成分特征、变质矿物组合以及它们的晶体化学成分所反映的变质温、压条件进行了研究,并在此基础上推断出该套变质岩属于由区域低温动力变质作用引起的低绿片岩相变质产物.
A sequence of slightly metamorphosed rocks is exposed between the western Kunlun northern margin deep fault and Tiekelike deep fault, along Aqike-Duwa-Sangzhu Reservior regions in Hotan of the southern margin of Tarim basin, covering an area of 140 km2 with a EW-trending length of 200 km and NS-trending width of 10-20 km. The rocks are mostly metamorphosed clastic rocks with metamorphosed minerals mainly of clorite, muscovite, quartz, and calcite and partly of biotite and Na-feldspar. A combined study of the slightly metamorphosed rocks at different localities in couple with petrogeochemistry, chemcial compositions of some metamorphic minerals, and metamorphic conditions, reveals that they have a rather constant lithology and rock association, and a corresponding metamorphic degree and deformation, as well as simple lithofacies. All these demonstrate that they are products of low greenschist metamorphism caused by regional low-temperature dynamic metamorphism. The outcropping Lower Proterozoic and Upper Devonian in the area have different metamorphic degree and lithological features from slightly metamorphose rocks. These rocks underwent another phase of metamorphism. The Ailiankate Group (Pt1a) of the Lower Proterozoic exposed south of Tiekelike fault have high greenschist metamorphism which is obviously higher than that of the slightly metamorphosed rocks north of the fault. The clastic rocks of Qizilafu Formation of the Upper Devonian contain small amount of clorite, sericite, quartz and calcite resulted from recrystallization or metamorphic crystallization, but the metamorphism only occurs within the cement and original texture is well preserved. It indicates that they are products of burial metamorphism of natrolite facies or grapestone-pumpellyite facies. No obvious metamorphism occurs within the Upper Carboniferous and overlying rocks. Therefore, the slightly metamorphosed rocks, its overlying Upper Devonian Qizilafu Formation, and Pt1a rocks are different in terms of their structural levels and degree of metamorphism. The previous correlation among these rocks needs reconsideration.
出处
《新疆地质》
CAS
CSCD
2002年第z1期38-42,共5页
Xinjiang Geology
关键词
塔里木南缘
浅变质岩系
变质矿物
变质条件
southern margin of Tarim
epimetamorphic rock series
metamorphic minerals
metamorphic condition
