摘要
东天山觉罗塔格地区广泛发育的晚古生代岩浆岩及相关的矿产一直是东天山大地构造研究的焦点。觉罗塔格南缘红云滩花岗质岩体的岩石、矿物组合显示典型的钙碱性火山弧花岗岩特征。岩石地球化学研究表明,该花岗质岩石富集大离子亲石元素而亏损高场强元素,是洋壳俯冲所导致的下地壳物质部分熔融、岩浆分离结晶和上地壳同化混染作用的产物。LAM-ICP/MS锆石定年结果表明,红云滩花岗岩侵位于早-中石炭世(328．5±9．3Ma)。结合觉罗塔格地区由南至北,晚古生代矿产分布由火山沉积-热液改造型铁矿向斑岩型铜钼矿过渡的特征、火山-沉积岩分布和该区晚古生代的大地构造演化历史,作者推测:早古生代觉罗塔格洋向塔里木板块俯冲并形成中天山岛弧之后,该洋盆并未完全消亡,并于晚古生代时极性反转,向北俯冲于准-吐-哈地块之下。红云滩花岗岩正是形成于晚古生代觉罗塔格俯冲洋壳之上的火山弧环境。觉罗塔格地区晚古生代的岩浆岩,火山-沉积岩和矿产分布均不同程度受控于这一大地构造背景。
Paleozoic igneous rocks and mineral deposits are keys to revealing the tectonic setting of the Qoltag belt in Eastern Tianshan, Xinjiang Province. Investigation in petrology, mineralogy and geochemistry indicates that the Hongyuntan granitoids at the southern margin of the Qoltag area are typical Calc-Alkaline volcanic arc granitoids, and have genetic relation with melting of the lower crust affected by subduction of the oceanic crust. U-Pb age determinations of Zircon by LAM-ICP/MS show the Hongyuntan granitoids were intruded at 328.5 ±9.3 Ma of Middle Carboniferous. By contrast, magmatism in the Middle Tianshan, south of the Qohag area is not important. In the late Paleozoic of the Qoltag area, mineral deposits show zonal distribution with its southern margin being dominated by Fe deposits of the volcanosedimentary and hydrothermal type, and its northern margin being dominated by Cu-Mo deposits of the porphyry type. In combination with distribution of the volcanosedimentary strata and tectonic evolution of the Qoltag and its surrounding areas, it is suggested that a Qoltag ocean occurred in the Paleozoic. In early Paleozoic, the Paleo-Qohag ocean subducted southward beneath the northern margin of the Tarim plate, resulting in the Middle Tianshan island arc. While in late Paleozoic, the Qohag ocean changed in subduction polarity and decent northward beneath the Junggar-turpan-Hami block. The Hongyuntan granitoids were thus formed in this volcanic arc setting above the subducting Qoltag ocean crust of late Paleozoic in association with other Hercynian magmatic rocks, volcanosedimentary strata, and zonally distributed mineral deposits.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第5期1121-1134,共14页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划项目(2001CB409802)
国家自然科学基金(40472042)联合资助.
关键词
花岗岩
年代学
觉罗塔格
东天山
新疆
Granitoids, Geochronology, Qoltag, Eastern Tianshan, Xinjiang, NW China
