A ca. 290 Ma hydrothermal calcite in Cambrian dolostone. (January 2023)

• Record Type: Journal Article
• Authors: Lan, Zhongwu; Wu, Shitou; Wang, Fangyue; Liu, Bo; Shi, Kaibo; Sun, Jing; Cao, Rong; Li, Xian-Hua
• Is Part Of: Marine and petroleum geology. Volume 147(2023)
• Publication Date: 2023-01
• Subjects: Hydrothermal calcite -- LA-ICP-MS U–Pb -- Tarim basin -- Ca. 290 Ma; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2022.106011
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: Acquiring the absolute timing for hydrothermal carbonate is a precondition to probing into the basinal-scale, tectonically-driven fluid circulation processes. This study provides an absolute LA-ICP-MS age of ca. 290 Ma from calcite megacrysts within the early Paleozoic dolostones of the Tarim Basin, which corresponds to the timing of Early Permian Large Igneous Province (LIP), which we suggest is genetically linked. The ca. 290 Ma calcite underwent subsequent partial recrystallization or dissolution-precipitation forming younger calcite ages of ca. 250 Ma, consistent with the timing of the Indosinian orogeny. Th/U ratios are demonstrated to be an effective criterion to differentiate domains of primary (ca. 290 Ma) and alteration (ca. 250 Ma) calcite, with the former displaying lower Th/U ratios (0.005-0.05) in comparison to the latter that shows relatively higher Th/U ratios (>0.15). Such differential Th/U ratios may suggest differential involvement of fluids from both within the host dolostones and from magmatic/hydrothermal fluids. This study also demonstrates that Si and Pb preferentially enter into the crystal lattice of calcite to replace Ca via charge balance substitution mechanism. In contrast, U, Sr, Y, La and Ce are mainly concentrated around cleavage planes, cracks and veinlets within calcite. Highlights: Recent years have seen the growing research interests that link hydrothermal carbonates with tectono-magmatic activity. Hydrothermal calcite is documented in Cambrian dolostone in Tarim Basin which yields a LA-ICP-MS U-Pb age of ca. 290 Ma. Age of the calcites is consistent with that of the ca. 290 Ma Tarim large scale magmatism, indicating their genetic links. Ca. 250 hydrothermal overprint induced higher Th/U ratios (>0.15) in the calcite.