Geochemistry of Preserved Permian Aragonitic Cements in the Tepees of the Guadalupe Mountains, West Texas and New Mexico, U.S.A.

摘要: Abstract Tepees are common depositional structures within the shelfal Capitanian Stage Yates and Tansill carbonate strata of Permian Reef Complex Guadalupe Mountains. As part tepees, botryoids radiating aragonite crystals formed essentially contemporaneously with host pisolitic strata. Although most cement in tepees is composed diagenetic low-magnesium calcite, X-ray diffraction analyses indicate that constitutes as much 27% centimeter-size patches. Back-scatter electron microprobe demonstrate a highly irregular pattern alteration partly preserved crystals. These patches aragonitic fibers have undetectable cathodoluminescence, Sr concentrations range up to 3,900 ppm, 87Sr/86Sr ratios from 0.70689 0.70695, which agreement worldwide marine values for Stage. Mass-balance calculations show some samples low-Mg calcite associated has over 2,300 ppm Sr; thus, diagenesis occurred under very low water-to-rock ratios. The least altered cements δ13C high 7.8‰ V-PDB (equivalent ~ 6‰ calcite) δ18O −5.5‰ −6.2‰ calcite). consistent whereas probably represent precipitation hot, equatorial, shallow tidal-flat environments. Contrary pathways displayed by carbonates, increasing generally resulted higher these relict aragonites. conclusively Paleozoic still