地幔的碳同位素

CARBON ISOTOPES IN MANTLE

近年来对金刚石、金伯利岩、碳酸岩、大洋玄武岩、地幔包体等地幔样品的碳同位素越来越多的研究发现，地幔碳的同位素主要集中分布在－５‰附近，而在－１５‰～－２５‰。区段有另一较弱的分布。目前的地幔碳的物相转变、沉积碳的俯冲和地幔去气等假说都很难解释这种碳同位素分布，原始地幔可能是碳同位素不均一的。

Recently,many carbon isotopic investigations for the mantle samples,such as diamond,kimberlites,carbonatites,oceanic basalts and mantle xenoliths,have shown that a very concentrated distribution is around -5‰,and a relatively weak distribution is from about -15‰ to -25‰ in the mantle carbon isotopes.This type of carbon isotopic distributions is difficult to explain by the current hypotheses,such as phase transformation of carboniferous matters,subduction of sedimentary carbon or mantle degassing,and so it is possible that the primordial mantle is heterogeneous in carbon isotopes.