The isotopic composition of sedimentary sulfur through time

The “chessboard” classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium

Minerals in the barite (BaSO4)–celestine (SrSO4) solid solution series, (Ba,Sr)SO4, occur in a remarkably diverse range of sedimentary, metamorphic, and igneous geological environments which span geological time from the Early Archean (~3.5 Ga) to the present. The purpose of this chapter is to review: (1) the controls on the chemical and isotopic composition of barite and celestine and (2) the geological environments in which these minerals form. Some health risks are associated with barite, and these are discussed near the end of this chapter.

Although complete solid solution exists between BaSO4 and SrSO4 most representatives of the series are either distinctly Ba-rich or Sr-rich. Hence, it is convenient to use the term barite to refer to not only the stochiometric BaSO4 endmember but also to those (Ba,Sr)SO4 solid solutions dominated by Ba. Similarly, the term celestine will refer here not only to the stoichiometric SrSO4 endmember but to solid solutions dominated by Sr. Such usage is in accord with standard mineral nomenclature. The Committee on Mineral Names and Nomenclature of the International Mineralogical Association recognizes “celestine” as the official name for SrSO4. However, the name “celestite” is still commonly used in the literature.

### Geological significance of barite and celestine

Most of the barite which exists in the Earth’s crust has formed through the mixing of fluids, one containing Ba leached from silicate minerals, and the other an oxidized shallow fluid, such as seawater, which contains sulfate. Large deposits of barite represent areas of focused fluid flow and mineral precipitation and thus aid in the reconstruction of the hydrogeologic history of the Earth’s crust. The stability of barite is redox sensitive, and the presence or absence of this mineral helps to constrain interpretation of paleoredox conditions. Pelagic barite, the precipitation of which is biologically mediated, may …

Barite–Celestine Geochemistry and Environments of Formation

The greatest loss of biodiversity in the history of animal life occurred at the end of the Permian Period (∼252 million years ago). This biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of Earth’s largest continental flood basalt provinces, the Siberian Traps. Volatile release from basaltic magma and sedimentary strata during emplacement of the Siberian Traps can account for most end-Permian paleontological and geochemical observations. Climate change and, perhaps, destruction of the ozone layer can explain extinctions on land, whereas changes in ocean oxygen levels, CO2, pH, and temperature can account for extinction selectivity across marine animals. These emerging insights from geology, geochemistry, and paleobiology suggest that the end-Permian extinction may serve as an important ancient analog for twenty-first century oceans.

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End-Permian Mass Extinction in the Oceans: An Ancient Analog for the Twenty-First Century?

Large shifts in the isotopic composition of seawater sulphate across the Permo–Triassic boundary in northern Italy

Sulfur and oxygen isotopes in Italian marine sulfates of Permian and Triassic ages

The barite-pyrite-iron oxides deposit of Monte Arsiccio (Apuane Alps); geological setting, mineralogy, fluid inclusions, stable isotopes and genesis

This paper deals with barite from stratiform, karst, and vein deposits hosted within Lower Paleozoic rocks of the Iglesiente-Sulcis mining district in southwestern Sardinia. For comparison sulfates from mine waters are studied. Stratiform barite displays δ34S=28.8−32.1‰, δ18O=12.7−15.6‰, and 87Sr/86Sr=0.7087, in keeping with an essentially Cambrian marine origin of both sulfate and strontium. Epigenetic barite from post-Hercynian karst and vein deposits is indistinguishable for both sulfur and oxygen isotopes with δ34S=15.3−26.4‰ and δ18O=6.6−12.5‰; 87Sr/86Sr ratios vary 0.7094–0.7140. These results and the microthermometric and salinity data from fluid inclusions concur in suggesting that barite formed at the site of mineralization by oxidation of reduced sulfur from Cambrian-Ordovician sulfide ores in warm, sometimes hot solutions consisting of dilute water and saline brine with different δ18O values. The relative proportion of the two types of water may have largely varied within a given deposit during the mineralization. In the karst barite Sr was essentially provided by carbonate host rocks, whereas both carbonate and Lower Paleozoic shale host rocks should have been important sources for Sr of the vein barite. Finally, δ34S data of dissolved sulfate provide further support for the mixed seawater-meteoric water composition of mine waters from the Iglesiente area.

Oxygen, sulfur, and strontium isotope and fluid inclusion studies of barite deposits from the Iglesiente-Sulcis mining district, Southwestern Sardinia, Italy

Oxygen-isotope variations in a barite slab from the sea bottom off southern California

A total of 42 C- and O-isotopic analyses on 35 samples of carbonates from pyrite and polymetallic deposits of southern Tuscany and associated country rocks are presented. Hydrothermal calcites and dolomites in the ore deposits show a wide range of isotopic compositions, which probably accounts for multiple sources of carbon and oxygen. Calculated isotopic compositions for COH species in equilibrium with calcites are similar to those measured in present-day geothermal fluids of the nearby Larderello-Travale field, suggesting a common link for all late- to post-Apenninic hydrothermal manifestations in the area. The isotopic compositions of country rocks range from typical marine values to lower values, the isotopic depletion likely accounting for metamorphic and hydrothermal effects related to the Mio-Pliocene Apenninic event. In contrast, 10 samples of similar rocks from non-mineralized areas of northern Tuscany show no isotopic evidence of metamorphic and hydrothermal alteration. Data from fluid inclusions indicate important relationships between calcite-forming fluids and sphalerite-forming fluids in the ore deposits here studied.

C- and O-isotope and fluid inclusion studies of carbonates from pyrite and polymetallic ore deposits and associated country rocks (southern Tuscany, Italy)

G. Cortecci

Papers

Sulfur and oxygen isotopes in Italian marine sulfates of Permian and Triassic ages

The barite-pyrite-iron oxides deposit of Monte Arsiccio (Apuane Alps); geological setting, mineralogy, fluid inclusions, stable isotopes and genesis

Oxygen, sulfur, and strontium isotope and fluid inclusion studies of barite deposits from the Iglesiente-Sulcis mining district, Southwestern Sardinia, Italy

Oxygen-isotope variations in a barite slab from the sea bottom off southern California

C- and O-isotope and fluid inclusion studies of carbonates from pyrite and polymetallic ore deposits and associated country rocks (southern Tuscany, Italy)