Trace-element and multi-isotope geochemistry of Late-Archean black shales in the Carajas iron-ore district, Brazil
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
The 250-300-m-thick Carajas Formation in the Carajas mineral province, northern Brazil, consists of banded iron formation (including giant high-grade iron-ore deposits) and minor black shale, overlying a thick pile (2-3 km) of about 2.75-Ga-old metabasalt. Carbonaceous shale with pyrite-and locally pyrrhotite-rich patches from drillcore of the Serra Sul exploration project has up to 29 ppm Mo; iron-speciation analysis indicates essentially ferruginous and for some samples likely euxinic depositional conditions. Positive delta S-34-isotope ratios of TRIS are between +0.3 to +10.7 parts per thousand, with heavy data restricted to pyrrhotite-free samples. The data suggest microbial sulfate reduction under, at least partially, sulfate-limiting conditions with later overprint by migrating solutions. The black shale is affected by pronounced low-temperature potassium metasomatism (K2O/Na2O > 100; up to 10 wt.% K2O as adularia) related to diagenetic processes at
Originalsprog | Engelsk |
---|---|
Tidsskrift | Chemical Geology |
Vol/bind | 362 |
Udgave nummer | SI |
Sider (fra-til) | 91-104 |
Antal sider | 14 |
ISSN | 0009-2541 |
DOI | |
Status | Udgivet - 20 dec. 2013 |
- Serra Sul, Carajas, Brazil, Black shale, Re-Os, Mo isotopes
Forskningsområder
ID: 119288975