西秦岭早子沟金矿中酸性侵入岩地球化学、年代学特征及成矿地质体的确定

Geochemical and chronological characteristics of intermediate-acid intrusive rocks in Zaozigou gold deposit, Western Qinling, and the determination of metallogenic geological body

西秦岭早子沟金矿是与岩浆活动有关的特大型金矿床,矿区中酸性侵入岩集中发育,主要有闪长玢岩、黑云石英闪长玢岩、花岗斑岩、石英闪长岩4种岩石类型。岩石微量元素均表现出富集大离子亲石元素Rb、K,亏损高场强元素Nb、Ta、P、Ti的特征。稀土元素总量整体上黑云石英闪长玢岩>闪长玢岩>石英闪长岩,闪长玢岩、黑云母石英闪长玢岩、花岗斑岩具有弱-中等的负铕异常(δEu=0.60~0.89),深部石英闪长岩以不具Eu异常(δEu=0.96~1.07)、“Nb-Ta谷”较深明显区别于浅部脉岩。石英闪长岩锆石U-Pb年龄为230 Ma,晚于浅部脉岩10~20 Ma,与蚀变矿物绢云母年龄基本一致,推测金成矿可能始于230 Ma,主成矿期为230~211 Ma,深部石英闪长岩为早子沟金矿的成矿地质体。

The Zaozigou gold deposit in the Western Qinling Mountains is a super-large gold deposit related to magmatic activity. The intermediate-acid intrusive rocks in the mining area are intensively developed, mainly including diorite porphyrite, biotite quartz diorite porphyrite, granite porphyry and quartz diorite. The trace elements in rocks are characterized by enrichment of large ion lithophile elements Rb and K, and depletion of high field strength elements Nb, Ta, P and Ti. On the whole, the total amount of rare earth elements in biotite quartz diorite porphyrite>diorite porphyrite>quartz diorite, diorite porphyrite, biotite quartz diorite porphyrite and granite porphyry have weak to medium negative europium anomaly( δEu = 0.60 ~ 0.89), deep quartz diorite has no Eu anomaly( δEu = 0.96 ~1.07), and “Nb-Ta valley” is deeper and obviously different from shallow vein rock. The zircon U-Pb age of quartz diorite is 230 Ma, which is 10 ~ 20 Ma later than that of shallow vein rock, and is basically consistent with the age of altered mineral sericite. It is speculated that gold mineralization may begin at 230 Ma, and the main mineralization period is 230 ~ 211 Ma. The deep quartz diorite is the metallogenic geological body of Zaozigou gold deposit.