| 对豆荚状铬铁矿床成因的认识 |
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| 引用本文：.1994.The origin of the podiform chromite deposits[J].Mineral Deposits,13(3):242~249 |
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| 中文摘要:文章提出豆荚状铬铁矿床不是上地幔局部熔融后的残余物，而是亏损地幔又经部分熔融形成的熔体发生液相不混熔，导致硅酸盐岩浆和富铬矿浆的形成。当比重不同高度分馏的熔体在上升过程发生了分离，轻熔体上升侵入于岩浆房、重熔体和铬铁矿浆，就地堆积或贯入围岩形成豆荚状铬铁矿床。豆荚状铬铁矿的伴生围岩纯橄岩，不是高度亏损的上地幔残余，可能是与铬铁矿浆伴随的一种硅酸盐熔体。与大量纯橄岩脉伴随的基性岩、超基性岩脉，也属不同程度熔融的产物。 |
| 中文关键词:铬铁矿 成因 豆荚状 |
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| The origin of the podiform chromite deposits |
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| Abstract:The podiform chromite deposits exhibit cumulate texture and occur in the Highly-depleted pyrolite of ophiolites. Nevertheless, they differ diametrically from their host rock in origin and hence are not residues after partial melting. Evidence shows that the podiform chromite deposits were formed by in-situ deposition of the upper mantle chromium-rich melt: 1)accessory picotite is obviously different from ore-forming picotite in variation trend of chemical composition; (2)there exist mineral and silicate melt inclusions in chromite deposits; 3)their PGE patterns are similar to the PGE patterns of stratiform chromite deposits formed by magmatic crystallization; 4)the mineral assemblage formed in the process of magmatic crystallization includes clinopyroxene, orthopyroxene, olivine and plagioclase. Although residual picotite might appear after partial melting, the formation of chromite deposits must have the prerequisite that the degree of partial melting should exceed 80％, but this is quite impossible in nature. There is merely a very small amount of chromium in the initial melt, and its concentration is thought to be the result of immiscibility between silicate melt and chromium-rich ore magma. Light silicatemelt which might have had basaltic composition ascended to form cumulate sequences of ophiolites, whereas denser and heavier chromium-rich ore magma was either crystallized in situ or intruded into the highly depleted pyrolite and then solidified to form podiform chromite deposits. |
| keywords:chromite, origin, podiform |
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