Wengao Zhang

右江盆地是中国重要的卡林型金矿及相关锑、铊、汞等低温热液矿床的集中分布区。为探究该区低温热液矿床成矿流体来源，本文以桂西龙滩金锑矿床首次发现的磁铁矿脉为研究对象，开展了矿物学、电子探针和电感耦合等离子体质谱等分析。结果显示龙滩磁铁矿与毒砂密切共生，具有高As（平均461 μg/g）和高Sb（平均427 μg/g）含量特征，且具有轻稀土相对富集（LREE/HREE平均值为7.1）的右倾型稀土配分模式，与右江盆地卡林型金矿含金黄铁矿具有相似的元素富集特征和稀土配分模式，暗示龙滩磁铁矿与金锑成矿作用为同一热液事件的产物。另外，龙滩磁铁矿还富集Al、Pb、V、Ti、Zn等微量元素，平均含量分别为6205 μg/g、1454 μg/g、877 μg/g、630 μg/g、201 μg/g。元素地球化学图解显示磁铁矿成因与岩浆作用相关热液流体相关，且有较高的沉淀温度（>500 ℃）。基于上述分析，本文认为桂西龙滩金锑矿床成矿流体与深部岩浆作用有关，暗示右江盆地卡林型金矿及相关锑、铊、汞等低温热液矿床的成矿流体可能具有岩浆成因。

Three-dimensional Mineral Prospectivity Mapping (3DMPM) is an innovative approach to mineral exploration that combines multiple geological data sources to create a three-dimensional (3D) model of a mineral deposit. It provides an accurate representation of the subsurface that can be used to identify areas with mineral potential. These 3D geological models are the typical data source for 3D prospective modeling. Geological data sets from multiple sources are used to construct 3D geological models. Since in practice there is a significant imbalance in the ratio of mineralized to non-mineralized classes, the classification results will be biased in favor of the more observed classes. Borderline-SMOTE (BLSMOTE) is an oversampling technique used to solve the problem of unbalanced datasets and works by generating synthetic data points along the boundary line between the minority and majority classes. This helps to create a more balanced dataset without introducing too much noise. Non-mineralized samples can be generated by randomly selecting non-mineralized locations, which means that uncertainties are generated. In this paper, we take the shallow-forming low-temperature hydrothermal deposit Guizhou Lannigou gold deposit as an example to extract the ore-controlling elements and establish a 3D geological model. A total of 50 training samples are generated using the sampling method described above, and 50 mineralization prospects are generated using Random Forests. A return–risk analysis was used to explore the uncertainties associated with synthetic positive samples and randomly selected negative samples, and to determine the final mineral potential values. Based on the evaluation metrics G-mean and F-value, the model using BLSMOTE outperforms the model without the synthetic algorithm and the models using SMOTE and KMeansSMOTE. The optimal model BLSMOTE18 has an AUC of 0.9288. The methodology also performs superiorly with different levels of class imbalance datasets. Excluding the predictions where the results highly overlap with known deposits, five target zones were circled for the targets using a P-A plot, all of which have obvious metallogenic geological features. Among them, Target1 and Target2 have good potential for mineralization, which is of great significance for future mineral exploration work.

The Jiadi gold deposit, situated in the Southwestern region of Guizhou, is a large-scale, recently discovered, basalt-hosted, and fine-grained disseminated gold deposit. This study has unveiled that the tectonic deformation of the Jiadi gold deposit can be categorized into four stages: the Late Paleozoic crustal uplift and brittle deformation (D1-deformation) stage; the Early Yanshanian NW-trending compressive ductile deformation (D2-deformation) stage; the Late Yanshanian NS-trending strike-slip fault (D3-deformation) stage; and the Himalayan EW-trending nappe structure (D4-deformation) stage. The outcomes of the C-O isotope analysis revealed that the fluid responsible for ore formation exhibits the attributes of magmatic water blended with meteoric water, and the metallogenic constituents primarily originate from a deep source. The formation of the Jiadi gold deposit occurred during the D2-deformation stage and extended to the D3-deformation stage. The D2-deformation stage induced hydrothermal activity and rock devolatilization, leading to the generation of CO₂-rich and low-salinity fluids. The D3-deformation stage, which is intimately associated with mineralization, can be classified into three stages: the pyrite stage; the smoky quartz stage; and the sulfide stage. The findings obtained from laser Raman spectroscopy indicate that the inclusions typically comprise CO_2, CH₄, N₂, and SO₂. These deep fluids ascended along the fault to the interlayer fracture zone during the D3-deformation stage. The alteration of the geochemical environment was accompanied by fluid immiscibility or boiling, resulting in the rapid precipitation of metallogenic materials.