| 中国造山带蛇绿岩中铬铁矿床的成因类型及其成矿的若干特征 |
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| 引用本文：.1992.Genetic types and some metallogenic characteristics of chromite deposits in ophiolites within phanerozoic orogenic belts of china[J].Mineral Deposits,11(1):21~34 |
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| 中文摘要:本文对我国造山带中铬铁矿床分为岩浆堆积成因及地幔熔融残余成因两大类型，并将它们细分为若干业类。两类铬铁矿分别产于蛇绿岩剖面的不同层位上，岩浆分离结晶成因者位于剖面的上部，地幔熔融残余成因的豆荚状铬铁矿床则位于剖面的下部。后者包括3个亚类，富铬型、富铝型及过渡型，它们具有不同的成因机制和成矿条件。 |
| 中文关键词:中国造山带蛇绿岩 地幔熔融残余成因 岩浆堆积成因 富铬与富铝型铬铁矿 |
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| Genetic types and some metallogenic characteristics of chromite deposits in ophiolites within phanerozoic orogenic belts of china |
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| Abstract:In this paper, chromite deposits in ophiolites of China’s Phanerozoic orogenic belts are classified into two major types consisting of several subtypes. One type refers to cumulate chromite deposits of magmatic origin, composed of two subtypes, i. e. Cr-rich subtype occurring in cumulates of Ol→Cpx→Pl sequence and A1-rich subtype existent in cumulates of Ol→Pl→Cpx sequence, which were formed respectively in high-pressure(magma chamber) and low-pressure(magma chamber)environments. The other type refers to podiform chromite deposits of mantle melting residual genesis and might be further divided into three subtypes, namely Cr-rich, A1-rich and transitional subtypes, which occur in their respective mantle residual assemblages, showing istinct melting zoning. The best ore-bearing petrofacies is dunite-Opx-poor zoned harzburgite complex in high-degree melting mantle residue. Both Cr-rich and A1-rich podiform chromite deposits are products of high-degree mantle melting. Their melting and ore-forming process was accompanied by two parallel evolutionary and reconstructive series. One was the progressive evolution of rock-forming minerals (Ol, Opx and Cpx) towards Mg enrichment with the gradual heightening of the melting degree(from lherzolite through harzburgite to dunite)j the other was the gradual evolution of accessory chrome spinel towards Cr enrichment with the progressive heightening of the melting degree. These evolutionary processes were accompanied by the corresponding change in textures and structures of minerals and rocks, leading eventually to the formation of two types of podiform chromite deposits with different components. The genetic difference between the Cr-rich chiomite deposit and the Al-rich one lies in the fact that the Al-rich chromite deposit was formed by the addition of large quantities of Al-rich melts caused by the complete melting of pyroxene at the late stage of mantle melting or at the beginning of the formation of dunite. The Al-rich melts led to the declining of Cr concentration in ore-bearing melts and eventually to the formation of the Al-rich chromite deposit. |
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