为什么火成岩地球化学需要地质学、岩石学和矿物学证据约束？-《地球科学与环境学报》

文章信息/Info

Title:: Why the Geochemistry of Igneous Rocks Needs Constraints by Geological, Petrological and Mineralogical Evidences?

Author(s):: LUO Zhao-hua; State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China

Keywords:: numerical petrology; magmatic mineral system; geochemistry of igneous rock; transmagmatic fluid; Fe-Ti oxide deposit; Sichuan

摘要:: 近年来，涌现了大量有关火成岩数值岩石学或化学岩石学的论文。但这不但没有导致科学问题的减少，反而出现了更多难以理解的难题。导致这种困境的主要原因是许多认识缺乏地质学、岩石学和矿物学约束，以及研究人员对火成岩理论研究进展的不关心。岩浆型矿床的成因是一个典型实例。基于此，分析了地球化学数据多解性的原因，介绍了岩浆系统的一般性质，并以四川攀西地区白马铁钛氧化物矿床为例，讨论了利用地质学、岩石学和矿物学证据约束地球化学数据的方法。在此基础之上提出：①全岩成分本质上不包含成因信息，相容元素的丰度可以表达岩石的潜在相组成，而不相容元素的丰度则可以表达岩石经历过的流体过程，因而数值岩石学只有得到严格的地质学、岩石学和矿物学约束才具有真实地质意义；②大型岩浆型矿床的形成同样需要巨量的含矿流体，透岩浆流体成矿模型可以更合理地解释白马铁钛氧化物矿床的成因。

Abstract:: Many contributions to the numerical or chemical petrology of igneous rocks are published in recent years. However, the volume of scientific issues is not decreased, but more and more problems are emerged. The major causes inducing such difficult condition are that many investigations are insufficient to be constrained by the geological, petrological and mineralogical evidences, and that many researchers do not concern to the developments in igneous theory. A typical example is the origin of magmatic deposit. Accordingly, the factors causing diversity of the geochemical interpretations were analyzed; the general features of magma systems were introduced; taking Baima Fe-Ti oxide deposit in Panxi area of Sichuan as an example, the methodology to constrain geochemical data by the geological, petrological and mineralogical evidences was discussed. The results show that ①the numerical petrology has real geological implications only then when it is constrained by geological, petrological and mineralogical evidences, because the bulk composition essentially do not include the genetic information about igneous rocks, but the compatible elements may present the potential phase proportion, and the incompatible elements may present the fluid processes undergone in rocks; ②the formation of giant ore deposit also needs a huge volume of the ore-bearing fluid, and hence, the transmagmatic fluid model can more reasonably explain the origin of Baima Fe-Ti oxide deposit.