不同气候带花岗岩风化过程中稀土元素的地球化学行为  

Geochemical Behavior of Rare-Earth Element During the Weathering of Granite under Different Climatic Conditions

作　　者：杨骏雄 刘丛强[1] 赵志琦[1] 丁虎[1] 刘涛泽[1] 涂成龙[1] 范百龄[1,2] 黄露[1,2] 

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室,贵州贵阳550002 [2]中国科学院大学,北京100081

出　　处：《矿物学报》2016年第1期125-137,共13页Acta Mineralogica Sinica

基　　金：国家自然科学基金重大国际合作项目(批准号:41210004);国家自然科学基金重点项目(批准号:41130536);国家自然科学基金面上项目(批准号:41173030)

摘　　要：本研究选择中国东部主要的花岗岩分布区中位于中温带、暖温带和热带的8个花岗岩风化壳作为研究对象,对比研究了不同气候环境下花岗岩风化过程中稀土元素(REE)的分布规律及其演化特征。结果表明,各气候带的花岗岩风化壳的REE分布具有一定的共性规律,风化产物的REE总量相对基岩都有不同程度的富集,且都表现出轻稀土(LREE)相对重稀土(HREE)富集以及一定程度的Eu负异常。由于REE的迁移和淋滤,导致其在风化壳内的再分配。通常REE在半风化层富集,p H值和粘土矿物含量等内因变化是导致这一现象的主要因素。对于少数表层REE富集的现象,如SD-DG、HN-3剖面,气候环境与地质条件等外因则是这一现象的主导因素。受海洋性气候影响显著的风化壳(QHD-1,HN-3),以基岩为标准,容易发生HREE富集的轻、重稀土分异的现象。大部分花岗岩风化壳中,Ce通常在剖面上部出现正异常,而在下部出现与之互补的Ce负异常。To illuminate the distribution and evolution characters of Rare Earth Element（REE） during granite weathering process under different climate conditions, this work examined eight profiles located in the main distribution area of granite from mid-temperate zone to tropic zone in Eastern China. Results show that the total concentrations（10^-6） of REE（ΣREE） of the weathered products were generally higher than those of the bed rocks in all places, and heavy REE（HREE） enriched relative to the light REE（LREE） while negative Eu anomaly were found more or less in all samples. During granite weathering process, REE have redistributed in the weathering crust due to REE migrating and leaching. Within the weathering profiles, REE leached form the upper layers and usually accumulated at the semi-weathering layers which resulted from variations of internal factors, such as p H and clay mineral content. In a few cases, the enrichment of REE at the upper layers in some weathering profiles such as SD-DG and HN-3, was mainly due to some external factors, such as climate condition and geology background. By the standard of parent rocks, HREE enrichment and differentiation between LREE and HREE were easily found in the granite weathering profiles which are strongly influenced by oceanic climate, such as QHD-1 and HN-2. Within the most granite weathering profiles in the current study, Ce showed the positive anomaly at the upper layers but complementary negative anomaly at the lower layers.

关 键 词：花岗岩风化壳 稀土元素 分异 气候 

分 类 号：P594[天文地球—地球化学] P595[天文地球—地质学]