EXPERIMENTAL GROWTH OF MVT SULFIDE MINERALIZATION

Mississippi Valley Type (MVT) deposits are a major Pb-Zn ore system. These deposits exist globally and are extremely important for access to mineral resources. MVT deposits are formed by saline ore brine solutions that precipitate the primary sulfide minerals. One of the leading hypotheses for precipitation is a model of fluid mixing, where metal-rich, sulfide-poor fluids mix with sulfide-rich, metal-poor fluids. While extensive analysis and modeling of MVT deposits have been done, very little work has been done experimentally recreating the mechanisms of MVT mineralization. This study aims to recreate the conditions of MVT mineralization by following a fluid mixing model to drive precipitation. Based on existing research of MVT deposits and fluids, simulated metal and sulfide fluids were prepared with chemical components in an effort to recreate the chemistry typical of saline MVT fluids. This utilized a combination of sodium, calcium, magnesium, and potassium chlorides. These fluids were combined to simulate the fluid mixing in MVT deposits as a precipitation mechanism. These experiments produced various minerals including metal sulfides such as galena, and associated minerals such as gypsum or pyromorphite. These were identified via Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM-EDS) analysis yielding compositional data which could be correlated with known mineral formulas. Through this analysis, the composition of individual crystals was characterized, and minerals identified based on composition and morphology from the SEM imaging. Comparing resulting mineral assemblages to the varied parameters for the reaction sets indicates parameters and conditions which can favor or hinder precipitation of MVT minerals and supports fluid mixing as a mineralization mechanism.