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一般认为,蚀变火山岩中的海水来源碳是太古代绿岩带中唯一主要的变质前的碳酸盐碳储库。因此,太古代金矿床中的碳酸盐由于稳定同位素比值太低(平均δ~(13)C=-3‰,不可能由这种C(通常认为其δ~(13)C近于0‰)生成,故被解释成是由某种局部的长英质岩浆源衍生出来的。但是,Barley和Groves(1987)在西澳大利亚的诺斯曼-威卢纳绿岩带中,识别出金矿化和区域变质前的两种碳酸盐蚀变类型,其证据归纳如下。这就是海底蚀变和受断裂控制的区域蚀变,如下所述,它们具有完全不同的碳同位素组成。后者(平均δ~(13)C=-4.8‰)意味着,在绿岩带演化期间,主要是来自地幔的岩浆碳(CO_2)流,因此其本身具有根本的重要性。然而,这里我们证明了只存在两种碳酸盐碳储库,以及在同一地区不同金矿床之间碳酸盐的碳同位素比值发生变化的原因,从而否定了某些通常用来支持岩浆流体模式的基本假设。
It is generally believed that seawater carbon in altered volcanic rocks is the only carbonaceous carbon reservoir in the Archean greenstone belt that is predominantly metamorphic. Therefore, the carbonates in the Archean gold deposit can not possibly be represented by this C (usually δ 13 C is close to 0 ‰) due to the low stable isotopic ratio (δ ~ (13) C = -3 ‰) Was interpreted as being derived from some locally felsic magmatic source, however, Barley and Groves (1987) identified gold mineralization in the Norseman-Willuna greenstone belt in Western Australia And the two types of carbonate alteration before regional metamorphism, the evidence is summarized as follows: This is the subarea alteration and regional alteration controlled by faults, which have completely different carbon isotopic compositions as described below.The latter δ ~ (13) C = -4.8 ‰) means that during the evolution of the greenstone belt, the flow of magmatic carbon (CO 2) from the mantle is mainly due to its fundamental importance.However, here we prove that there is only The two carbonate carbon reservoirs, and the reason for the change in the carbon isotope ratio of carbonates between different gold deposits in the same area, negate some of the basic assumptions that are commonly used to support magma fluid models.