Acta Petrologica et Mineralogica

Mississippi Valley-type (MVT) lead-zinc deposits are closely related to evaporite rocks, however, the fact that evaporite minerals dissolve or transform into other minerals and "disappear" is often overlooked. Drawing on previous research results, we summarized the transformation and identification characteristics of evaporite, and its relationship with MVT Zn-Pb mineralization that is reflected in the source of mineralizing fluids, the source of sulfur, and the ore-bearing structures. The formation of MVT deposits involves basin brines, primarily derived from evaporated seawater, with a small portion originating from the dissolution of evaporite rocks. Meanwhile, the deve-lopment of regional evaporite rocks indicates the formation conditions for mineralizing fluids. The sulfur in lead-zinc metal sulfides totally comes from the reduction of sulfates, and evaporite minerals, such as gypsum, anhydrite, etc., are important suppliers of sulfates. Moreover, dissolution-collapse evaporites form breccias and collapse spaces, and lead-zinc mineralization can occur within the breccias and/or adjacent strata. Salt diapiric structures create favorable structural/chemical traps for fluid accumulation and mineral precipitation, and lead-zinc mineralization can be found in the caprock, transition zones and peridiapiric rocks of salt diapirs, vertically oriented salt diapiric breccia pipes, or top of domes formed by lateral salt diapirism. Pseudomorphs after evaporite minerals and residual evaporite minerals are direct evidence of the existence of "disappeared" evaporites, while minerals such as albite and scapolite, length-slow chalcedony/quartz, alkali-enriched double-terminated quartz, etc., may indicate the past existence of evaporites. The evaporite dissolution-collapse structures exhibit the characteristics of lateral extension along with the stratigraphic strike, and salt diapiric structures have features such as cross-cutting and breccias derived from lower strata, both of which can help identify evaporite-related structures. In exploration for MVT deposits, the regional stratigraphic record of evaporative sedimentary environments is necessary for MVT mineralization, and evaporite dissolution-collapse structures as well as salt diapiric structures are important prospecting targets.

evaporite; MVT deposit; brine; source of sulfur; dissolution-collapse structure; salt diapir