Carbon isotopic compositions of pore and matrix carbonates in carbonate nodules, and origin of carbonate formation

作     者：LIU Lian YIN QiuZhen WU HaiBin GUO ZhengTang 

作者机构：Key Laboratory of Cenozoic Geology and Environment Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China Institut d'Astronomie et de Geophysique G. Lemaitre Universite catholique de Louvain Chemin du Cyclotron 2 1348 Louvain-la-Neuve Bel gium 

出 版 物：《Chinese Science Bulletin》 (中国科学通报)

年 卷 期：2010年第55卷第26期

页      面：2926-2929页

核心收录：

学科分类：070704[理学-海洋地质] 0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 0707[理学-海洋科学] 

基　　金：supported by the National Basic Research Program of China (2010CB950200) the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-117) the National Natural Science Foundation of China (40730104) 

主　　题：碳同位素组成 碳酸盐结核 核基质 中国黄土高原 碳同位素分析 起源 测量误差 同位素方法 

摘      要：Carbon isotopes of pedogenic carbonate are often used to study paleoenvironments, but the existence of detrital carbonate changes the carbon isotopic composition. To develop an experimental method to determine existence of detrital carbonate in carbonate nodules, and to avoid it during isotope analysis, 23 pedogenic carbonate nodules in Miocene loess from the Loess Plateau of China were studied through micromorphology and carbon isotope analysis. The difference in carbon isotopic composition between matrix carbonate (B) and pore carbonate (A) (δ 13C(B-A)) ranges from 0.27‰ to 0.44‰ in nodules containing detrital carbonate and -0.16‰ to 0.13‰ in nodules where detrital carbonate is absent. The latter is within measurement error, but the former is beyond it. Here we propose an isotopic approach to determine if nodules contain detrital carbonate: if δ 13C(B-A) is within the measurement error, the nodules do not contain detrital carbonate, and vice versa. We suggest that it is better to analyze pore carbonate instead of matrix carbonate when using carbon isotope of carbonate nodules to reconstruct paleoenvironments.