库车坳陷早始新世短暂海侵演化史:来自锶同位素的证据  

The evolution history of the early Eocene transient transgression in the Kuqa Depression:Evidence from strontium isotopes

作　　者：曾锡泽 徐洋 张华[3] 黄振宁 ZENG Xize;XU Yang;ZHANG Hua;HUANG Zhenning(College of Earth Sciences,East China University of Technology,Nanchang Jiangxi 330013,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang Jiangxi 330013,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China)

机构地区：[1]东华理工大学地球科学学院,江西南昌330013 [2]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [3]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《矿物学报》2024年第6期889-897,共9页Acta Mineralogica Sinica

基　　金：第三次新疆综合科学考察(编号:2022xjkk1303);成矿作用与资源评价重点实验室开放基金(编号:ZS2203);新疆维吾尔自治区重大科技专项项目课题一(编号:2022A03009-1)。

摘　　要：塔里木盆地在白垩纪-古近纪主要识别出5次海侵-海退旋回,其中晚古新世-早始新世海侵事件是规模最大的一次。目前对于库车坳陷早始新世海侵演化史的研究还比较薄弱,尤其是通过碳酸盐岩锶同位素手段对其开展研究还尚未涉及。本文通过对库车坳陷西部小库孜拜剖面下始新统蒸发岩段进行岩相学特征分析和碳酸盐岩锶同位素组成研究,以期探讨该地区早始新世海侵演化历史。根据岩相学特征和蒸发岩沉积序列变化,认为早始新世库车坳陷气候炎热干燥,主要发育障壁潟湖相。研究表明小库孜拜剖面下始新统灰岩锶同位素组成介于0.708627~0.708909之间,略高于同时期海水锶同位素值(0.7077~0.7078),远低于同期陆源锶同位素值,结合泥晶灰岩镜下特征和锶同位素特征,本文认为该时期主要以海水沉积为主,伴有少量陆源物质输入。对比小库孜拜组灰岩和西藏岗巴地区碳酸盐岩锶同位素组成演化曲线和硫同位素组成变化,推测早始新世库车坳陷发生一次短暂的海侵事件,海平面变化原因可能是对全球海平面变化的响应。Five major transgression-regression cycles during the period from Late Cretaceous to Paleogene have been identified in the Tarim Basin.The Late Paleocene-Early Eocene transgression event is the largest one among them.At present,the research on the evolution history of the early Eocene transgression in the Kuqa Depression is still relatively limited,especially has not been undertaken by means of strontium isotope of carbonate rocks.In this paper,the lithofacies characteristics and strontium isotopic compositions of carbonate rocks within the Lower Eocene evaporate section of the Xiaokuzibai profile in the western Kuqa Depression have been studied in order to explore the evolution history of the early Eocene transgression in this area.Based on the petrographic characteristics and the sedimentary sequence of evaporites,it is believed that the early Eocene climate was hot and dry,and the barrier lagoon facies were mainly developed in the Kuqa Depression.The study shows that the strontium isotopic compositions of the Lower Eocene limestone samples in the Xiaokuzibai profile vary from 0.708627 to 0.708909,which are slightly higher than the strontium isotopic values(0.7077-0.7078)of seawaters in the same period,but are far lower than those of terrestrial materials in the same period.Combined with the microscopic and strontium isotopic characteristics of micrite,that seawater deposits were mainly deposited in this period with a small amount of terrigenous materials,it is suggested that there was mainly seawater deposition in the area,with accompanied input of a small amount of terrestrial materials.Comparing the evolution curves of strontium and sulfur isotopic compositions of limestones in the Xiaokuzibai Formation and carbonate rocks in the Gamba area of Tibet,it is speculated that a short transgression event occurred in the Kuqa Depression in the early Eocene,and the reason for sea level change in the area may be responded to the global sea level change.

关 键 词：锶同位素 碳酸盐岩 海平面变化 库车坳陷 

分 类 号：P579[天文地球—矿物学] P611[天文地球—地质学]