The origin and diagenesis of grain-coating serpentine-chlorite in Tuscaloosa Formation sandstones, U.S. Gulf Coast

Other| February 01, 1996 The origin and diagenesis of grain-coating serpentine-chlorite in Tuscaloosa Formation sandstones, U.S. Gulf Coast P. C. Ryan; P. C. Ryan Dartmouth College, Department of Earth Sciences, Hanover, NH, United States Search for other works by this author on: GSW Google Scholar R. C. Reynolds R. C. Reynolds Search for other works by this author on: GSW Google Scholar American Mineralogist (1996) 81 (1-2): 213–225. https://doi.org/10.2138/am-1996-1-226 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation P. C. Ryan, R. C. Reynolds; The origin and diagenesis of grain-coating serpentine-chlorite in Tuscaloosa Formation sandstones, U.S. Gulf Coast. American Mineralogist 1996;; 81 (1-2): 213–225. doi: https://doi.org/10.2138/am-1996-1-226 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Randomly interstratified serpentine-chlorite (Sp-Ch) is ubiquitous in sandstones of the subsurface Tuscaloosa Formation. The Sp-Ch occurs as grain coatings, pore fillings, peloids, and infillings. The presence of peloids and infillings suggests that the Sp-Ch originated as odinite, a 7 Å mineral that forms at the sediment-seawater interface in shallow, tropical marine sediments. We conclude that during the very earliest stages of diagenesis, odinite peloids and infillings transformed to mixed-layer Sp-Ch, forming grain coatings with preservation of some of the original odinite textures. The formation of grain-coating Sp-Ch during early diagenesis apparently preserved high primary porosity in medium-grained specimens. Fine-grained and silty sandstones, however, contain poorly formed grain coatings and are tightly cemented by quartz, implying that grain size also has some effect on authigenic quartz growth.With increasing burial depth between 1702 and 6216 m, the proportion of Sp layers in Sp-Ch decreases from 20.7 ± 1.1 to 1.3 ± 0.1%, indicating that Sp layers transform to Ch layers with increasing diagenetic grade. The polytype of the Sp-Ch is essentially Ibb at depths <2000 m. At depths >2000 m, the polytype is randomly interstratified Ibb-Iaa, and the proportion of Ibb layers decreases from -100 to 49% over the interval studied. At depths <2000 m, orthohexagonal Sp transforms to Ibb Ch, but at depths >2000 m, orthohexagonal Sp transforms to Iaa Ch. There is essentially no change in Sp-Ch chemical composition with depth, implying that temperature is the dominant control on the structural transformations. Mean crystallite thickness also remains relatively constant with increasing depth, indicating that diagenetic transformations in Sp-Ch do not involve crys-tal-growth mechanisms typical of most clay minerals. Rather, the mineralogic transformations appear to proceed on a layer-by-layer basis, with individual layers dissolving and reprecipitating within the confines of the crystallites. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.