Carbon isotope geochemistry of graphite deposits and ore-bearing khondalite series in North China: implications for several geoscientific problems.

本文综合了中国北方孔达岩系和石墨矿床的碳同位素数据 10 2件 ,发现片麻岩石墨 透辉岩石墨 <大理岩石墨 <石墨大理岩方解石 <大理岩方解石 ;混合岩化岩石中石墨δ1 3C总介于有机碳和无机碳之间 ;不同地体片麻岩石墨δ1 3C极为一致 ,变化于 - 2 2 .8‰～ - 2 1.48‰ ,略低于世界有机质平均值 - 2 6± 7‰ ;大理岩的原岩碳酸盐δ1 3C高于 2‰ ,与2 330～ 2 0 6 0 Ma期间全球性δ1 3Ccarb正向漂移事件一致。地质流体是碳同位素分馏、均一化的重要因素 ,是石墨矿床的 3种主要碳源之一 ,是碳的 5种存在形式之一 ,也是碳循环的重要媒介和方式 ...A database of 102 analyses of delta(13)C(PDB) for graphite deposits and ore-bearing khondalite series in North China clearly shows several regularities: 1) delta(13)C(gneiss graphite)<<delta(13)C(diopsidite) (graphite)<delta(13)C(marble) (graphite)<delta(13)C(graphite-marble) (calcite)<delta(13)C(marble) (calcite;) 2) the values of delta(13)C(migmatite graphite) are always between those of organic carbon and inorganic carbon; 3) the averages of delta(13)C(gneiss graphite) for different terrains, ranging from -22. 8 parts per thousand to -21. 48 parts per thousand, are consistent completely, and slightly lower than the average of -26+/-7 parts per thousand for organic matter from the world; 4) delta(13)C for the protolith of marble is estimated over 2 parts per thousand, which is consistent with the worldwide delta(13)C(carb) positive excursion in the period of 2330 similar to 2060 Ma. Conclusions are drawn out as below: (1) geofluid is an important constraint on fractionation and homogenization of carbon isotopes, one of three carbon sources for graphite mineralization, one of five existing forms of carbon, and a key media and style of carbon circulation as wen; (2) it is unbelievable that, only stemmed from delta(13)C(calcite)congruent to-5 parts per thousand, ore-forming fluid and material for hydrothermal deposits are derived from mantle, because many factors can cause hydrothermal delta(13)C(calcite) equal to about - 5 parts per thousand; (3) the khondalite series in North China are mainly developed in Paleoproterozoic, most likely, in the period of 2300 similar to 2050 Ma.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000088761800013&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701SCI(E)中文核心期刊要目总览(PKU)中国科学引文数据库(CSCD)3102233-2441