甘肃省龙首山成矿带芨岭岩体闪长岩特征及其与铀成矿关系

芨岭岩体是龙首山铀成矿带加里东期岩浆岩，其闪长岩侵位于加里东早期，是芨岭岩体主要岩石类型之一。闪长岩主要有两期侵入，分别为早期灰色、深灰色中粒闪长岩以及晚期深灰色细粒闪长岩，且出露面积较小，集中分布于新水井、芨岭地区。采用LA ICP MS方法对研究区内中粒闪长岩进行锆石U Pb测年，得到年龄值为(4856±14) Ma。研究表明，闪长岩对后期铀成矿起重要作用：破碎蚀变闪长岩作为一种优质赋矿岩石，为含矿热液提供了卸载空间，蚀变后矿物成分主要为钠长石、绿泥石、方解石、赤铁矿等蚀变矿物，同时随着U含量的增加蚀变闪长岩中SiO2含量略有增加，Na2O明显增加，K2O、FeO 和P2O5有下降的趋势，CO2含量先增后减。综合研究分析认为，闪长岩本身是钠交代型铀矿的有利赋矿岩石，而其与花岗岩的接触面为花岗岩内接触带铀矿富集提供了物理化学环境突变的成矿结构面

Characteristics of Diorite from Jiling Pluton and Its Relationship with Uranium Metallogenic in Longshou Mountains,Gansu Province

Jiling pluton is Caledonian magmatic rock in Longshoushan uranium ore belt. Diorite is one of the main rock types of Jiling pluton, which emplaced in the Early Caledonian. Diorite is mainly distributed in Xinshuijing and Jiling area;the early diorite is gray dark gray medium grained; while the later one is dark gray fine grained.This investigation obtains (4856±14) Ma as the age of the medium grained diorite by LA ICP MS zircon U Pb dating. The research shows that the diorite plays an important role in later uranium metallogeny. The altered diorites provide the U bearing hydrothermal fluids for unloading space. There are albite, chlorite, calcite, and hematite in altered diorite. With increasing of U content, SiO2 content is a bit increasing while Na2O increasing obviously; the K2O,FeO and P2O5 contents are obviously decreasing; and CO2 content increases at first and decreases when U content is much higher, but it is slightly increasing overall. By comprehensively studying and analyzing, the diorite is regarded as a favorable host rock to sodium metasomatic uranium, and the contact belt of diorite and granite provides a physicochemically sharply changing setting as a physicochemical barrier for the uranium enrichment.