云南鹤庆锰矿碳氧同位素特征分析

云南鹤庆锰矿位于扬子地台西南缘，对其岩石样品的碳氧同位素分析表明，上三叠统松桂组经历了一次海进和一次漫长的海退期。生物(藻类)代谢与海水发生同位素交换、古气候环境的变化和古海水深度的变化都使反演的古温度偏高；古盐度分析显示正常海相沉积特征，略低的盐度与碳同位素偏低有关。钻孔样品的氧同位素主要由盐度变化而产生一个高值范围，且对应碳同位素低值区，由于海平面下降，有机质埋藏率低导致碳同位素向负值漂移。根据以上分析认为，沉积时期的环境至少是一个半局限的浅海近陆源盆地，伴随扬子地台不断抬升，气候由潮湿、炎热转变为干燥的大陆性气候，锰矿的形成也是伴随海退海水变浅而沉积成矿。

Characteristics of Carbon and Oxygen Isotope in Heqing Manganese Deposit,Yunnan, China

Heqing manganese deposit is located in the southwestern margin of Yangtze platform in Yunnan Province,China.Carbon and oxygen isotopes indicate that Songgui Formation which is the main ore bearing stratum experienced one transgression and another long-term regression.The paleotemperature derived from oxygen isotopes are higher due to the exchange of oxygen isotope between biological(algae) metabolites and seawater,changes in paleoclimate and sea depth.The paleosalinity show normal marine sediments and there are good correlation between the paleosalinity and the value of δ13C.δ18O values from cores are higher mainly owing to the variation of paleosalinity,which are good correlation with δ13C value.With the sea level falling,the possibility of buried organic was decreased,which led to negative values of δ13C.Through a comprehensive analysis of carbon and oxygen isotopes,it is concluded that the depositional environment was at least a semi-enclosed shallow or near continental basin.With uplifting of Yangze platform continuously and climate changing from humid,hot into arid gradually,the manganese ores were formed accompanied by falls in sea level.