广西大厂矿田泥盆系地层地球化学及其成矿指示

成永生^{1, 2, 3}，黄惠明⁴

(1. 中南大学 有色金属成矿预测教育部重点实验室，长沙 410083；
2. 中南大学 地球科学与信息物理学院，长沙 410083；
3. 中国科学院 地球化学研究所 矿床地球化学国家重点实验室，贵阳 550002；
4. 广西二一五地质队有限公司，柳州 545006)

摘 要：利用岩石地球化学的理论与方法，对大厂矿田的主要赋矿地层泥盆系中、上统开展了主量元素地球化学、稀土元素地球化学以及微量元素地球化学的分析与研究，对泥盆系地层与大厂矿田矿床与矿产的关系进行了探讨，阐述了泥盆系的有利成矿条件及其对矿床的关键控制作用。结果表明，泥盆系地层主量元素成分为SiO₂、CaO、Al₂O₃、Fe₂O₃、MgO、Na₂O以及K₂O等，以SiO₂和CaO为主体，其中，纳标组地层CaO含量最高，其余各组地层SiO₂含量均表现为不同程度的偏高，这与大厂矿区泥盆系地层的岩性特征以及岩石组合密切相关。利用Al₂O₃—SiO₂岩石热水成因模式显示，泥盆系形成过程中沉积环境多变，岩石物源具有多来源的特点，也从一定程度上导致了泥盆系地层多样化的岩性特点以及复杂的岩石建造。泥盆系ΣREE含量变化于(2.9~318.77)×10^-6之间，其中，纳标组地层表现出轻、重稀土元素亏损，罗富组地层则表现为轻、重稀土元素富集。泥盆系地层的微量元素组成主要包括Ba、Rb、Sr、Th、U、La、Ce、Pr、Nd等。泥盆系不同组地层独特的岩石类型与岩性组合，是金属成矿元素发生富集的有利因素。

关键词：大厂；泥盆系；地球化学；控矿因素；成矿作用

Geochemical characteristics and mineralization indication of Devonian strata in Dachang ore field, Guangxi

CHENG Yong-sheng^{1, 2, 3}, HUANG Hui-ming⁴

(1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry,
Chinese Academy of Sciences, Guiyang 550002, China;
4. Guangxi No. 215 Geological Party, Liuzhou 545006, China)

Abstract:Based on the theory and method of the petrogeochemistry, the major element, REE and trace element of the Middle and Upper Devonian in the Dachang orefield were analyzed, the relationship between the Devonian and minerals was discussed, the favorable metallogenic conditions and its critical control to the ore deposit were also elaborated. The results suggest that the major elements of the Devonian consist of SiO₂, CaO, Al₂O₃, Fe₂O₃, MgO, Na₂O and K₂O, yet SiO₂ and CaO are dominant. The calcium oxide content of Nabiao formation is the maximum, but the SiO₂ content of the other formations seems to be too high in different degrees, which closely relates to the lithological characteristics and rock assemblage of Devonian in Dachang orefield. According to the hydrothermal mode of Al₂O₃-SiO₂, the depositional environment of Devonian was variable with multiple sources, which led to the diverse lithology and complex rock formations. The content of ΣREE of Devonian is 2.9×10^-6-318.77×10^-6, among which the Nabiao formation depletes LREE and HREE elements, yet the Luofu formation relatively enriches LREE and HREE elements. The trace elements of Devonian are composed of Ba, Rb, Sr, Th, U, La, Ce, Pr and Nd. The special rock type and lithological combination of Devonian are the favorable factors for the metal enrichment.

Key words:Dachang; Devonian; geochemistry; ore-controlling factor; mineralization