大兴安岭地区花岗岩风化过程中锂同位素地球化学行为  

Lithium isotope geochemical behavior in the weathering process of granites in the Greater Khingan Mountain area,northeastern China

作　　者：张俊文 闫雅妮 孟俊伦 章倬君 赵志琦 ZHANG Jun-wen;YAN Ya-ni;MENG Jun-lun;ZHANG Zhuo-jun;ZHAO Zhi-qi(School of Earth Science and Resources,Chang'an University,Xi'an 710054,China;Sichuan Keyuan Testing Center of Engineering Technology Co.Ltd.,Chengdu 610059,China;Key Laboratory of Watershed Geographic Sciences,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,China)

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]四川省科源工程技术测试中心有限责任公司,成都610059 [3]中国科学院南京地理与湖泊研究所,流域地理学重点实验室,南京210008

出　　处：《矿物岩石地球化学通报》2023年第4期873-881,共9页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(41930863,42003007);陕西省自然科学基金资助项目(2022JZ-19,2022JQ-229)。

摘　　要：锂(Li)同位素具有示踪大陆风化的潜力,但风化体系中Li同位素组成(δ7Li)对风化强度的指示关系仍不明确。本文以大兴安岭地区花岗岩风化剖面为研究对象,采集了剖面不同风化层位的样品,测定了原岩及其风化产物样品的元素含量和δ7Li值。结果表明,风化剖面上部的δ7Li值为-0.08‰~+1.8‰,中下部的δ7Li值为-2.6‰~+0.25‰并低于原岩的值(+0.75‰)。δ7Li值在剖面上部的变化主要是黄土输入及其再风化的结果,而中部主要是受次生矿物溶解和再沉淀过程的影响,下部主要是受控于次生矿物形成过程。岩石风化产物的Li同位素组成可以作为风化强度的替代指标,但次生矿物溶解和再沉淀过程可能会影响风化剖面的δ7Li值对风化强度的指示关系。The lithium isotopes has potential for tracing the continental weathering process. However, the relationship between Li isotopic composition(δ~7Li) and weathering intensity in the weathering system remains unclear. In this study, samples from various weathering zones of a granite weathering profile in the Greater Khingan Mountain area(in the northeastern China) have been collected to determine the elemental contents and δ~7Li values of samples including the original rock and weathering products of the profile. The results show that δ~7Li values of samples in the upper part of the weathering profile vary from-0.08‰ to +1.8‰,and those of samples in the middle and lower parts of the profile vary from-2.6‰ to +0.25‰, which are lower than that of original rock(+0.75‰). The variation of δ~7Li values of samples in the upper part of the profile was mainly resulted from the loess input and re-weathering process, while the variation of δ~7Li values of samples in the middle part of the profile was mainly influenced by the secondary mineral dissolution and re-precipitation processes, but the variation of δ~7Li values of samples in the lower part of the profile was mainly controlled by the secondary mineral formation process. Our results above indicate that the Li isotopic composition of rock weathering product can be used as a proxy indicator for the weathering intensity, but secondary mineral dissolution and re-precipitation processes could affect the role of δ~7Li values of samples in the weathering profile for tracing the weathering intensity of rocks in the profile.

关 键 词：花岗岩 风化壳 锂同位素 次生矿物 外源物质 大兴安岭 

分 类 号：P597[天文地球—地球化学]