甘肃红石泉地区基性岩脉特征及Ar-Ar定年

基性岩脉是研究地幔和地幔变化的"窗口"，并且与金、铀、金刚石等矿床有重要关系.甘肃红石泉地区产有我国最典型的白岗岩型铀矿床，其中发育有多条基性岩脉.研究区基性岩新鲜面呈灰绿色，具有典型的煌斑结构，块状构造，斑晶矿物主要为角闪石，基质主要由斜长石和黑云母组成，副矿物主要有磁铁矿、磷灰石及锆石等，据此确定基性岩为闪斜煌斑岩.岩石具有富碱、高钾、贫铁以及富集轻稀土元素和大离子亲石元素等地球化学特征，进而判断其属于钾质钙碱性煌斑岩.通过40Ar-39Ar全岩测定，获得煌斑岩成岩年龄为237.2±2.6 Ma，煌斑岩的岩浆来源于EMII型富集地幔，形成于板内拉张环境，岩浆在上升侵位过程中遭受了地壳物质的混染，属于早中生代古亚洲洋闭合、陆陆碰撞后伸展的产物.红石泉煌斑岩与铀矿床铀成矿没有直接成因关系，对于铀矿只有后期改造作用. 

Characteristics and Ar-Ar Dating of Mafic Dykes in Hongshiquan Area,Gansu Province

The basic vein is a "window" for studying mantle and its evolution, and has important relationship with gold, uranium, diamond deposits and the others. The most typical alaskite type uranium deposit in China occurs in Hongshiquan area of Gansu Province among which there are a number of basic veins. The fresh surface of the basic rocks in the study area is gray-green, with typical lamprophyre structure, and massive structure. The porphyry minerals are mainly hornblende, the matrix mainly is composed of plagioclase and biotite, and accessory minerals are mainly magnetite, apatite, zircon etc.. Based on this characteristics, it is determined that the basic rock is diorite lamprophyre. The characteristics of elemental geochemistry ascertain that the lamprophyres are rich in alkali, high in potassium, poor in iron, and enriched in LREE and LILE, indicating that they belong to potash calc-alkaline lamprophyres. The whole-rock 40Ar-39Ar dating yields a lamprophyre diagenetic age of 237.2±2.6 Ma. The magma of the lamprophyre originated from EMII-enriched mantle and formed in the intraplate extensional environment. The magma was contaminated with crustal materials during the process of rising emplacement, which was the product of the extension following closure of the Late Asian Paleozoic Paleo-Asian Ocean and continental collision. There is no direct genetic relationship between the uranium metallogenesis of the Hongshiquan lamprophyre and the uranium deposit, but only late-stage transformation of uranium deposits.