豫西南泥湖地区辉长岩地球化学特征及其与成矿关系

Geochemical Characteristics and Its Relationship with Mineralization of Gabbro in Nannihu Area

摘要:

豫西南泥湖钼矿集区是以花岗斑岩体为中心的钼多金属矿床系列，区内出露大面积加里东期变辉长岩和燕山期辉长岩。通过分析区内辉长岩的岩石学、年代学、地球化学和成矿元素等方面特征，研究其在成岩成矿过程中的作用。区内加里东期变辉长岩和燕山期辉长岩成矿元素总稀土含量低，稀土元素球粒陨石标准化曲线右倾平缓，具有明显的Eu，Tm元素的异常；同比世界基性岩，自晚元古代上地幔主要成矿元素（除钨元素以外）基本没有明显的富集，主成矿元素钼含量呈明显的亏损，预示燕山期成矿花岗质岩浆没有从上地幔获得主要成矿物质。初步认为大规模的钼多金属成矿带的形成与基性岩浆的底垫作用相关，基性岩浆的底垫作用为下地壳部分熔融形成岩浆房提供了热源。

Abstract:

Nannihu molybdenum ore area is a series of molybdenum polymetallic deposits centering on the granite porphyry. A large area of Caledonian metagabbros and Yanshanian gabbros distributed in this area. Through analyzing petrology, chronology , geochemistry and ore forming elements of gabbros，mechanism and mineralization of the magmatism have been studied. The total rare earth content of oreforming element in metagabbros and Yanshanian gabbros of Caledonian period is low. The chondritenormalized REE patterns incline to the right gently, and showing obvious Eu and Tm abnormal. Comparing with basic rocks from all over the world, main oreforming elements of upper mantle have no obvious enrichment except for W since late proterozonic period in this area. Main mineralizing elements, such as Mo, seems to have significant losses. It is showed that granitic magma of Yanshanian gabbros do not get metallogenic substances from the upper mantle. It is inferred that the formation of the scale of the molybdenum polymetallic metallogenic belt is related to basic magmatic underplateing. It will provide heat source for partial melting in the lower crust.