Antigorite-ophicarbonates: Phase relations in a portion of the system CaO-MgO-SiO2-H2O-CO2期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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Antigorite-ophicarbonates: Phase relations in a portion of the system CaO-MgO-SiO2-H2O-CO2

Authors:	Volkmar Trommsdorff Bernard W Evans

Institution:	(1) Institut für Kristallographie und Petrographie, ETH, Sonneggstraße 5, CH-8006 Zürich, Switzerland;(2) Department of Geological Sciences, University of Washington, 98195 Seattle, Washington, USA

Abstract:	The occurrence of critical assemblages among antigorite, diopside, tremolite, forsterite, talc, calcite, dolomite and magnesite in progressively metamorphosed ophicarbonate rocks, together with experimental data, permits the construction of phase diagrams in terms of the variables P, T, and composition of a binary CO₂-H₂O fluid. Equilibrium constants are given for the 30 equilibria that describe all relations among the above phases. Ophicalcite, ophidolomite, and ophimagnesite assemblages occupy partially overlapping fields in the $T - X_{{\text{CO}}_{\text{2}} }$ diagram. The upper temperature limit of ophicalcite rocks lies below that of ophidolomite and ophimagnesite. The fluid phase in ophicarbonate rocks has $X_{{\text{H}}_{\text{2}} {\text{O}}} > 0.8$ , and there are indications that $P_{{\text{H}}_{\text{2}} {\text{O}}} + P_{{\text{CO}}_{\text{2}} }$ during their progressive metamorphism is approximately equal to P _total.

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