中温带气候区花岗岩风化剖面元素地球化学特征及其环境意义  

Elements geochemical characteristics and environmental significance of granite weathering profiles in the middle temperate zone

作　　者：刘若男 迟云平[1,2] 谢远云[1,2] 康春国[3] 吴鹏 孙磊 汪烨辉 Liu Ruonan;Chi Yunping;Xie Yuanyun;Kang Chunguo;Wu Peng;Sun Lei;Wang Yehui(College of Geographic Science,Harbin Normal University,Harbin 150025;Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions,Harbin Normal University,Harbin 150025;Geography Department,Harbin institute,Harbin 150086)

机构地区：[1]哈尔滨师范大学地理科学学院,哈尔滨150025 [2]哈尔滨师范大学寒区地理环境监测与空间信息服务黑龙江省重点实验室,哈尔滨150025 [3]哈尔滨学院地理系,哈尔滨150086

出　　处：《地质科学》2023年第4期1373-1393,共21页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:42171006,41601200);黑龙江省自然科学基金项目(编号:D2017003);哈尔滨师范大学学术创新项目(编号:HSDSSCX2022-07);哈尔滨师范大学博士启动基金项目(编号:XKB201418)资助。

摘　　要：岩石风化是地球关键带中重要的地质过程,对环境变化具有重要的指示意义。不同气候区岩石风化过程具有其特殊性,本文选取位于中温带气候区的哈尔滨英杰花岗岩风化剖面为研究对象,通过元素地球化学特征分析,揭示岩石风化程度及元素迁移富集规律,并结合磁化率和色度指标,对其风化环境进行探讨。结果表明,研究区剖面整体化学风化程度较低(CIA值为56~68);Ca、Na、K等活动性较强元素随风化作用的进行表现为明显亏损;高场强元素与轻稀土元素也表现出较强的活动性,揭示了即使在中低等程度的化学风化下稳定元素也容易迁移。Si/Al和Ti/Al比值指示半风化层和腐泥岩层为原位风化产物,而顶部的氧化土层则可能受外来物质的影响。化学风化表现为自下而上逐渐减小的特征,这种异常的风化规律是由后期物理风化对其原有化学风化的叠加改造所致。对风化环境的多指标分析表明,在风化剖面形成后,区域气候逐渐变干,化学风化向物理风化转变,温差风化及冰劈作用形成大量裂隙导致原有的风化剖面被改造,并最终形成了研究区独特的风化模式,这为解释中温带气候区干冷环境下花岗岩风化特征提供了新的思路。Rock weathering is an important geological process in the critical zone,which has important indicative significance for environmental change.The rock weathering process in different climate zones has its particularity.In this study,the weathering profile of Harbin Yingjie granite located in the middle temperate climate zone is selected as the research object.The degree of rock weathering and the rule of element migration and enrichment are revealed by analyzing the geochemical characteristics of elements.Meanwhile,the weathering environment was discussed by combining the magnetic susceptibility and chromaticity indexes.The results showed that the overall chemical weathering degree of the profile was low(CIA value ranged from 56 to 68).The active elements such as Ca,Na and K showed obvious loss with the weathering process.High field strength elements and light rare earth elements also show strong activity,revealing that stable elements are easily migrated even under medium to low degrees of chemical weathering.The Si/Al and Ti/Al ratios indicate that the semi-regolith and saprolite layers are in situ weathering products,while the oxide layer at the top may be affected by foreign materials.The characteristic of chemical weathering is decreasing from bottom to top.This abnormal weathering rule is caused by the superposition of physical weathering on the original chemical weathering.The multi-index analysis of weathering environment shows that after the formation of the weathering profile,the regional climate gradually becomes dry.The chemical weathering to the physical weathering,the thermal weathering and frost action formed a large number of cracks,resulting in the transformation of the original weathering profile,and finally formed a unique weathering mode in the study area,which provides a new idea for explaining the characteristics of granite weathering in the middle temperate zone.

关 键 词：花岗岩 中温带 化学风化 元素地球化学 气候环境 

分 类 号：P512.1[天文地球—地质学] P595