The Black Angel deposit, Greenland: a Paleoproterozoic evaporite-related Mississippi Valley-type Zn–Pb deposit

• Published in: Mineralium Deposita
• Main Authors: Rosa, Diogo, Leach, David, Guarnieri, Pierpaolo, Bekker, Andrey
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2023
• Subjects: Life Below Water; MVT Zn-Pb deposits; Paleoproterozoic; Evaporites; Greenland; Paleoproterozoic seawater sulfate level; Geochemistry; Geology; Geophysics
• Online Access: https://escholarship.org/uc/item/7pz782tk; https://escholarship.org/content/qt7pz782tk/qt7pz782tk.pdf; https://doi.org/10.1007/s00126-022-01125-z

AbstractThe Paleoproterozoic Mârmorilik Formation in the Karrat basin of West Greenland hosts the Black Angel Zn–Pb deposit. Chlorine-rich scapolite, zones with vuggy porosity and quartz nodules in the ore-bearing marble are herein interpreted to represent metamorphosed, vanished, and replaced evaporites, respectively. Mineralization is closely associated with anhydrite with δ34S values (5.2–12.6‰) broadly comparable to published values for Paleoproterozoic seawater sulfate. Considering the fundamental attributes of the mineralization and host sequence, a Mississippi Valley-type (MVT) model is the most obvious explanation for mineralization. Overlying the ore-bearing sequence are organic-rich semipelites and massive calcitic marbles, which may have served as seals for hydrocarbon or reduced sulfur and acted as chemical traps for deposition of the sulfidic ore. The Mârmorilik Formation contained an interlayered sulfate-rich evaporite-carbonate sequence, a common setting for MVT deposits in the late Neoproterozoic and Phanerozoic, but unique among the few known MVT deposits in the Paleoproterozoic. This ca. 1915Ma evaporite-carbonate platform is younger than sulfate evaporites deposited during and immediately after the ca. 2220–2060Ma Lomagundi carbon isotope excursion and records a significant seawater sulfate level during a time interval when it was assumed that it had been too low to form extensive evaporite deposits. Therefore, MVT and clastic-dominated (CD) Zn–Pb deposits in the geological record might progressively fill the apparent gap in marine sulfate evaporites and provide unique insights into Proterozoic seawater sulfate level. Considering the sequence of tectonic events that affected the Karrat basin, the mineralization took place between Nagssugtoqidian collision (< 1860Ma) and Rinkian metamorphism (ca. 1830Ma).