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九个泉蛇绿岩作为北祁连山加里东造山带中最具代表性的蛇绿岩残片之一,很早就引起了人们的关注.应用SHRIMPⅡ锆石U-Pb法,对蛇绿岩中的均质辉长岩进行了精确测年,18组测试数据给出的206Pb/238U加权平均年龄为(490±5.1)Ma(MSWD=1.06),该年龄代表了辉长岩的结晶年龄,同时也应代表九个泉蛇绿岩的形成年龄.地球化学研究表明,该蛇绿岩上部的玄武岩-辉绿岩单元具有典型N-MORB特征和弱的俯冲带印记.根据九个泉蛇绿岩的年龄数据和地球化学资料,认为九个泉蛇绿岩很有可能是北祁连弧后盆地洋脊扩张的产物.九个泉蛇绿岩形成环境的判定和形成时代的确定为北祁连山早古生代洋内俯冲体系的发育和演化,以及古构造格局提供了重要制约。
As one of the most representative ophiolite fragments in the Caledonian orogenic belt in the North Qilian Mountains, Jiuquanquan ophiolite has aroused people’s attention for a long time.Using the SHRIMPⅡ zircon U-Pb method, The homogenized gabbro has been accurately dated, and the 206Pb / 238U weighted average age (1890 ± 5.1) Ma (MSWD = 1.06) given by the 18 sets of test data represents the age of gabbro, as well as Should represent the age of formation of nine spring ophiolites.Geochemical studies indicate that the basaltic-diabase units in the upper part of the ophiolite have typical characteristics of N-MORB and weak subduction zone mark.According to the Age data and geochemical data, it is concluded that Jiuquanquan ophiolite is probably the product of the oceanic ridge expansion in the North Qilian arc back basins.The determination and formation age of Jiuquanquan ophiolite is determined by the Early Paleozoic The development and evolution of the oceanic subduction system and the palaeo-tectonic setting provide important constraints.