Abstract The Vazante Group comprises a Proterozoic sequence of carbonate and siliciclastic rocks located in Minas Gerais, Brazil. It is the host of the Vazante-Paracatu Zinc District, including world-class hypogene zinc silicate deposits, in the southern part, and several Pb – Zn sulfide deposits in the northern part, all hosted in dolomitic rocks. A recent study revealed the occurrence of base metal sulfide mineralization that formed prior to the Brasiliano orogenic event in the siliciclastic rocks (Serra do Garrote Formation) that underlie these dolomite-hosted silicates and sulfide deposits. These siliciclastic rocks were considered as potential sources of elements for the hydrothermal fluids that formed the dolomite-hosted deposits, however there was little evidence of depletion of the source rocks during the orogenic event. In this paper, Random Forest is used in unsupervised mode along with t-distributed Stochastic Neighbor Embedding (t-SNE) and principal component analysis (PCA) over a lithogeochemical dataset of samples of the Serra do Garrote siliciclastic rocks collected throughout the basin to provide insights about processes related to the mineralizing system at the Vazante-Paracatu District. Multivariate analysis reveals that the Serra do Garrote Formation geochemical signature typical of pre-orogenic mineralization. This is characterized by PC1+ with association of Zn, Cd, Cu, Hg, In, V ± Sb, Se, Mo, Re, which corresponds to nearly 60% of the variance in the data. This suggest that these elements are related to a widespread and/or, long-living hydrothermal activity without an efficient mechanism to focus the metal-bearing fluids, causing basin-scale sub-economical Zn and related metal enrichment. Furthermore, PC2 and PC6 distinguish the zones with signatures interpreted to be related to depletion. PC2+ separates Cd-poor sphalerite, which is typical of the generation of sphalerite that occur in zones with textural evidence of remobilisation. PC6+ with association of As, organic carbon and S, identified the zones where sphalerite was leached from the pyrite-rich layers. Areas with multivariate signatures of both pre-orogenic enrichment and syn-orogenic depletion in the source siliciclastic rocks include the Vazante-North Extension and Varginha zinc silicate deposits/occurrence, Ambrosia silicate zinc deposit and the Engenho Velho prospect. Preliminary exploration in this prospect revealed hydrothermal alteration typical of the zinc silicate deposits. This study is pioneering in applying these numerical models in possible source rocks to assist in identifying targets for exploration in basins.

中文翻译：

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分析地球化学数据以发现知识的多变量组合方法：巴西米纳斯吉拉斯州瓦赞特 – 帕拉卡图锌区

摘要 Vazante 群由位于巴西米纳斯吉拉斯州的一个元古代碳酸盐岩和硅质碎屑岩层序组成。它是瓦赞特-帕拉卡图锌矿区的所在地，包括南部世界一流的下成因硅酸锌矿床和北部的几处铅锌硫化物矿床，均赋存于白云岩中。最近的一项研究揭示了在巴西利亚诺造山事件之前形成的贱金属硫化物矿化在硅质碎屑岩（Serra do Garrote 组）中形成，这些岩层是这些以白云岩为主体的硅酸盐和硫化物矿床的基础。这些硅质碎屑岩被认为是形成白云岩赋存矿床的热液流体的潜在元素来源，但是几乎没有证据表明在造山事件期间烃源岩枯竭。在本文中，随机森林在无监督模式下与 t 分布随机邻域嵌入 (t-SNE) 和主成分分析 (PCA) 一起用于整个盆地收集的 Serra do Garrote 硅质碎屑岩样品的岩石地球化学数据集，以提供有关相关过程的见解到 Vazante-Paracatu 区的矿化系统。多变量分析表明，Serra do Garrote 地层具有典型的造山前矿化特征。这表现为 PC1+ 与 Zn、Cd、Cu、Hg、In、V ± Sb、Se、Mo、Re 的关联，这对应于数据中近 60% 的方差。这表明这些元素与广泛和/或长期存在的热液活动有关，而没有一种有效的机制来集中含金属流体，导致盆地规模的次经济锌和相关金属富集。此外，PC2 和 PC6 区分具有解释为与耗尽相关的特征的区域。PC2+ 分离了贫镉闪锌矿，这是典型的闪锌矿生成，发生在具有再动员纹理证据的区域。PC6+ 与 As、有机碳和 S 的结合，确定了闪锌矿从富含黄铁矿的层中浸出的区域。在源硅质碎屑岩中具有造山前富集和同造山耗竭的多元特征的区域包括 Vazante-North Extension 和 Varginha 硅酸锌矿床/产地、Ambrosia 硅酸盐锌矿床和 Engenho Velho 勘探区。该远景区的初步勘探揭示了典型的硅酸锌矿床的热液蚀变。