西南天山托云盆地古近纪熔积岩成因及其古环境意义  

Petrogenesis and Paleoenvironmental Significance of Paleogene Peperite in the Tuoyun Basin,Southwestern Tianshan Mountains

作　　者：刘帆 程志国[1] 郭祝芳 冀文涛 LIU Fan;CHENG Zhiguo;GUO Zhufang;JI Wentao(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)地质过程与矿产资源国家重点实验室,北京100083

出　　处：《现代地质》2025年第1期46-61,共16页Geoscience

基　　金：国家自然科学基金面上项目(42072067)。

摘　　要：熔积岩是一种由炙热的熔岩流与湿冷沉积物混合形成的特殊火山碎屑岩,主要由浆源碎屑和宿主沉积物两部分构成。其独特的成因和产出环境为岩浆喷发期的沉积环境研究提供了重要依据。西南天山托云盆地记录了中生代以来塔里木湾海退的地质演化,新发现的古近纪熔积岩揭示了区域海陆转换过程。本研究以托云熔积岩为对象,通过典型剖面宿主碳酸盐岩的主微量元素和碳氧稳定同位素分析,探讨其古环境特征。分析结果显示,宿主碳酸盐岩的δ^(13)C_(VPDB)变化范围为-4.05‰~-7.74‰,δ18OVPDB变化范围为-6.42‰~-11.93‰。基于经验公式计算,其形成的古环境温度为30.3~6.9℃,古盐度指数为114.6~105.5(平均为110.2),古盐度值为24.77‰。综合研究表明,该熔积岩形成于海陆边界的微咸水潟湖环境。Peperite is a distinctive pyroclastic rock formed by the interaction between hot lava flows and cold,moist surface sediments.Composed of juvenile clasts and host sediments,its unique origin and occurrence provide critical insights into paleoenvironmental conditions during volcanic eruptions.The Tuoyun Basin,located in the southwestern Tianshan Mountains,preserves geological evidence of the regression of the Tarim Bay since the Mesozoic.The recent discovery of Paleogene peperite in the Tuoyun Basin has been interpreted as a key marker of the transition from marine to terrestrial depositional environments.This study investigates the major and trace element compositions,along with the carbon and oxygen isotopic characteristics,of host carbonates associated with the Tuoyun peperite.The results show that theδ^(13)C_(VPDB) values of the host carbonates range from-4.05‰to-7.74‰,while theδ18OVPDB values range from-6.42‰to-11.93‰.Based on empirical calculations,the estimated paleotemperature of peperite formation spans from 30.3℃to 6.9℃,with a paleosalinity index ranging between 114.6 and 105.5(average of 110.2),corresponding to a paleosalinity of 24.77‰.These findings suggest that the Tuoyun peperite formed in a slightly brackish lagoonal environment located at the marine-terrestrial interface during the Paleogene.

关 键 词：托云盆地 熔积岩 始新世 古环境 白云岩 

分 类 号：P581[天文地球—岩石学] P588.211[天文地球—地质学]