Minerals with Mixed Anion Radicals in Fumarole-Transformed Crush Microxenolites as a New Phenomenon of Modern Volcanism

Abstract

Microxenoliths of sedimentary-marine carbonatoliths in fumaroles of the crater zone of the Second Cone of the BTFE Northern Breach, which were exposed to exhalative-pneumatolytic fluids with the formation of many compounds with mixed carbonate-sulfate-chloride anionic radicals, which are considered as two interclass and nine intertype crystal chemical hybrids, are studied at the expense of carbonates. The pattern of heterogeneity of mineral parasteresis revealed in the altered microxenoliths is interpreted by us as the result of a successive epigenetic transformation of primary carbonates, first into sulfate-carbonates, then into carbonate-sulfates, and then into chloride-carbonate-sulfates and chlorides. Judging by the absence of signs of phase heterogeneity, the investigated crystal-chemical hybrids are homogeneous solid-phase mixtures of carbonates, sulfates, and chlorides in different proportions. The carbonates in microxenoliths in terms of carbon isotope composition (δ13СPDB = –5.34 ± 0.62‰) and oxygen (δ18OSMOW = 24.09 ± 1.05‰) correspond to carbonates of sedimentary-marine limestones redeposited under conditions of volcanic transport. The isotopic composition of sulfate sulfur (δ34S = 1.5–2‰) varies within the range of fluctuations established for sulfates of volcanogenic origin. In carbon particles associated with microxenoliths, the isotopic compositions of carbon (δ13CPDB = –27.37 ± 2.97‰) and nitrogen (δ15NAir = 6.74 ± 2.48‰) tend to be similar to the mode of distribution of such values in the products of modern continental volcanism. The identified crystal-chemical hybrids are a typomorphic feature of the fumarous-exhalative facies and are considered as a previously unknown phenomenon of modern volcanism.