摘要
以柯坪塔格组灰绿色砂岩为研究对象,开展了系统的岩石地球化学和同位素年代学研究。结果表明,砂岩SiO_2质量分数较高,Na_2O、CaO、TiO_2质量分数较低;轻稀土元素富集,具明显的Eu负异常。碎屑锆石U-Pb年龄集中分布于1 000~700,2 500~1 800 Ma 2个区间,可能分别对应新元古代晚期南华纪-青白口纪的构造抬升运动和古元古代早期的强烈构造运动及岩浆侵位,个别锆石颗粒年龄超过2 500 Ma,2颗锆石年龄数据偏小,仅在437~435 Ma之间,可能与南天山洋俯冲导致的岩浆活动有关。分析表明,早志留世柯坪地区处于稳定的被动大陆边缘,碎屑物源主要来自塔北隆起前寒武纪古老的克拉通基底岩类。
Taking gray-green sandstone of Kepingtage Formation for research objects, systematic geochem- ical and isotopic geochronological analyses are applied. Results suggest that there are high content of SiO2 and low content of Na2 O, CaO and TiO2. ∑ LREE〉 ∑ HREE, abnormity of Eu is negative. U-Pb ages of zircons concentrate in 1 000--700 Ma and 2 500--1 800 Ma, which may corresponding to tectonic uplifting events occurred during Late Proterozoic Nanhua to Qingbaikou Period and magmatic emplacement couple with intense tectonic movements during Paleoproterozoic. Several U-Pb ages of zircons over 2 500 Ma,may be related to remelting of Archeozoic strata. Two U-Pb ages of zircons between 437 Ma to 435 Ma may be related to magmation resulted from southward subduction of the South Tianshan Ocean. Analyses show that the Keping area was situated on a passive continental margin during Early Silurian. Sedimentary rocks are mainly sourced from Pre-Cambrian basement rocks in Tabei area, mixing with several granit zircons from Early Silurian.
出处
《地质科技情报》
CAS
CSCD
北大核心
2017年第2期1-12,共12页
Geological Science and Technology Information
基金
中国地质调查局西北沿边及特殊地区地质矿产调查二级项目(DD20160079)
