贵州老万场金矿成矿物质来源的研究

SOURCE OF ORE-FORMING MATERIALS IN LAOWANCHANG GOLD ORE DEPOSIT, GUIZHOU PROVINCE, CHINA

硅酸盐成分研究表明老万场红土化过程经历了粘土化、铝土矿化、铁化三种化学风化作用;风化中化学蚀变较强,K2O、Na2O、CaO相对于Al2O3的淋失量很高。在红土剖面上成矿元素的含量变化很大。相关性分析表明,红土化过程中,Au、As的富集与脱硅富铝化程度关系不大,而与铁的富集有明显的关系;Au、As的富集与相对还原的环境有关,而Sb则在相对氧化的环境中易于聚集。可能反映了红土剖面中潜水面下部附近相对还原的环境Au、As易于富集。大厂层样品和老万场红土剖面样品在成矿元素(Au、As、Sb)含量、稀土元素含量、轻重稀土比值、配分曲线上以及微量元素特征包括大离子亲石元素、不相容元素上的较大差异,显示了红土层的发育与大厂层岩石有较大的差别,暗示它们物质来源上的一定差异性。

Variations in Silicate composition of a laterization profile in the Laowanchang gold deposit revealed that three chemical weathering processes occurred during laterization in this region. Stronger chemical alteration could also be observed during the process, with stronger leaching of K_2O, Na_2O and CaO as compared with Al_2O_3. Au, As and Sb concentrations varied greatly along the lateritic profiles. Results of correlation analysis showed that during laterization, the enrichment of Au and As has little bearing on desilicification and Al enrichment, but has a great bearing on Fe enrichment. Enrichment of Au and As is usually related with relatively reductive circumstance, but Sb with relatively oxidative circumstance, which can be observed from the phenomena of Au and As enrichment at lower water table in the lateritic profiles where relatively reductive circumstance exists. Great differences for Dachangceng samples and Laowanchang lateritic profile samples can be described in the following aspects: REE contents, ratios of LREE to HREE, REE distribution patterns, and trace element features such as large ion lithophile elements and incompatibility elements constitution; differences for ore-forming elements also exist, which implies the Dachangceng rocks did not directly offer ore-forming materials for lateritic development in the Laowanchang region.