Nodular celestite in the Chihsia Formation (Middle Permian) of south China

Abstract

The middle Permian Chihsia Formation of south China accumulated on a shallow shelf, and consists mainly of black to dark grey micritic limestone rich in chert nodules and organic matter. A unique type of nodular crystal cluster is distributed widely in the carbonate succession. Most crystal clusters consist of calcite. Some, however, are composed of celestite, and geochemical, microscopic and crystal morphological data suggest that celestite was the precursor of the calcite. The celestite developed displacively within the sediments during early diagenesis, before compaction and before local dolomitization of the host rock. Similar strontium isotopic values were obtained from the celestite clusters, replacement calcite, vein calcite and host rock. The values are within the range of middle Permian sea water. The strontium in the celestite was furnished chiefly by either diagenetic alteration of strontium‐rich marine aragonite to strontium‐poor calcite, or aragonite dissolution induced by aerobic oxidation of organic matter, or both. The sulphur isotopic values of the celestite are about 6–11‰ heavier than the sulphur isotopic value of sulphate in coeval sea water. Based on geological context, this difference is attributed to microbial reduction of porewater sulphate in the Chihsia sediments.

Early diagenetic celestite replacement of demosponges in Upper Cretaceous (Campanian–Maastrichtian) chalk, Stevns, Denmark

“…Marine evaporites that could have supplied the isotopically heavy sulfur are not present in the chalk succession, so the most likely source for the sulfate is sea water. However, the enrichment of 8.7‰-16.4‰ relative to coeval seawater is comparable to that reported from early diagenetic celestite nodules, where the sulfur source is interpreted to be microbial reduced porewater sulfate (Yan and Carlson, 2003).…”

“…Nodular celestite associated with deeper water carbonates has been reported from Deep Sea Drilling Project (DSDP) Leg 90, where they were interpreted to have formed as the result of submarine burial diagenesis (Baker and Bloomer, 1988), and from the Permian of south China, where they formed in shelf carbonates during early diagenesis (Yan and Carlson, 2003). None of these nodules were directly related to organisms.…”

Miocene diagenetic and epigenetic strontium mineralization in calcareous series from Cyprus and the Arabian Gulf: Metallogenic perspective on sub- and suprasalt redox-controlled base metal deposits

“…Ca isotope ratios were calculated from mass spectrometric raw data. Strontium isotope analyses are commonly used in the study of celestite deposits (Yan and Carlson, 2003, further literature cited therein) and a sound basis for the 87 Sr/ 86 Sr ratios of seawater is available for the Neogene through the comprehensive paper of Howart and McArthur (1997). As a first for celestite deposits, 44 Ca/ 40 Ca and 44 Ca/ 42 Ca isotope ratios have been determined for carbonate and sulphate rocks (see DePaolo (2004) and Fantle and DePaolo (2005) for an overview of the geological application of Ca isotope methods).…”

Phosphorite-hosted zinc and lead mineralization in the Sekarna deposit (Central Tunisia)

“…The close association of celestite with evaporates is attributed to sulfate enrichment in evaporated pore waters or by the dissolution of evaporites, or else as a consequence of the transformation of aragonite to calcite and/or dolomite during early diagenesis (e.g., Yan and Carlson 2003). No evaporite sequences have been observed in Sekarna area, nor have evaporates been recognized in the sedimentary record at Sekarna.…”