引用本文：李久明,周可法.2019.塔吉克斯坦东杜奥巴金矿床岩脉矿体岩石学、地球化学及成矿年代学研究[J].地质学报,93(1):197-214. LI Jiuming,ZHOU Kefa.2019.The research of petrology geochemistry and geochronology of ore- bearing granitic in Dongduaoba gold deposit, Tajikistan[J].Acta Geologica Sinica,93(1):197-214.
The research of petrology geochemistry and geochronology of ore- bearing granitic in Dongduaoba gold deposit, Tajikistan
1） Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, Xinjiang, China；2） Tbea Co., Ltd., Changji, Xinjiang, 831100, China
1） Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, Xinjiang, China
Abstract:Dongduaoba Gold Orefield is located in the western part of the system of folds in south Tianshan of Central Asia Orogenic Belt. The ore- bearing magmatic rock in this field is represented by NW- SE directionally distributed apophysis or vein- like exposed. The magmatic rock is mainly composed of subalkaline- intermediate- acidic monzonite, monzogranite and adamellite. Some rocks are ore- bearing, and play some controlling role in mineralization. In this research, 6 ore- bearing magmatic rock samples were collected to carry out whole- rock geochemical analysis, and LA- ICP- MS zircon U- Pb dating analysis on 4 of these 6 samples; on this basis, the diagenetic mineralization time frame and tectonic environment were determined. These samples are mainly Al- Pertarenite rocks of subalkaline- high- k of ca- alkaline，which are belong to monzonite- adamellite. The content of SiO 2 , K 2 O, Na 2 O, ALK, solidification index (SI), differentiation index (DI), alkalinity ratio (AR) and Rittmann index ( σ ) ranges from 57.34%~64.13%, 3.40%~4.65%, 3.29% to 6.17%, 7.13%~9.57%, 10.42~19.95, 65.75~94.06, 2.2~3.78 and 2.52~5.54 respectively. The total content of rare earth elements is low, and ΣREE is between 60.93×10 -6 ~133.37×10 -6 . There is significant differentiation between light and heavy REEs.These rocks can be represented by a normalized REE distribution curve of right- handed chondrites. However, HREE curves are relatively flat. (La/Yb) N =5.45~22.53, (La/Sm) N =2.46~4.28. LILEs like K, Rb and U are accumulated while HFSEs like Nb, Ta, P and Ti are depleted, Hf, La and Ce shows positive anomalies while Sr shows negative anomalies. Additionally, the negative Eu is not very significant ( δ Eu=0.23~0.35), indicating that the source area may contain many depleted mantle components. Besides, major elements of the rocks represent the characteristics of crust type and crust- mantle type, indicating possible addition of mantle- derived material in the process of magma evolution. LA- ICP- MS zircon U- Pb dating results show that the 206 Pb/ 238 U weighted average age of 4 ore- bearing rock samples is 284.8±2.1Ma（MSWD＝2.2）, indicating that the ore- bearing magmatic in Dongduaoba Gold Orefield was formed in the Early Permian. Based on the regional geological background, it is believed that the mineralization in the region occurred in the semi- mature island arc environment of the Late Paleozoic Active Continental Margin, and the formation of subalkaline- intermediate- acidic magmas was of great significance to the formation of gold ore.