Nodular celestite in the Chihsia Formation (Middle Permian) of south China
Article first published online: 15 APR 2003
Volume 50, Issue 2, pages 265–278, April 2003
How to Cite
Yan, J. and Carlson, E. H. (2003), Nodular celestite in the Chihsia Formation (Middle Permian) of south China. Sedimentology, 50: 265–278. doi: 10.1046/j.1365-3091.2003.00552.x
- Issue published online: 15 APR 2003
- Article first published online: 15 APR 2003
- Manuscript received 18 August 2000; revision accepted 19 November 2002.
- Chihsia Formation;
- nodular celestite;
- south China;
- strontium isotopes;
- sulphur isotopes
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.