Barite in omphacite-hosted K-feldspar ＋ quartz polycrystalline aggregates from the Sulu eclogites and its implications

K-feldspar quartz polycrystalline aggregates were found as sub-millimeter-size inclusions with a pseudomorph after coesite (?) in omphacites from a number of Sulu eclogites. In these aggregates, round or subhedral barites occur as tiny inclusions in either K-feldspar or quartz. Energy dispersive spectroscopy (EDS) analyses show that these barites have (1) 33.86%―41.12% SO3, 0%―34.65% SrO, and 24.12%―63.55% BaO, (2) seemingly negative linear correlations between SrO and BaO, indicating that they are ideal solid solutions of barite (BaSO4) and celestite (SrSO4), and (3) highly variable Sr/Ba molar ratios ranging from 0 to 2.1. Presence of barites in the Sulu eclogites not only indicates oxidation of the subducting continental crust, but also very limited and restricted fluids pre- sented during exhumation of the Sulu UHP eclogites.

Barite in omphacite-hosted K-feldspar + quartz polycrystalline aggregates from the Sulu eclogites and its implications

K-feldspar + quartz polycrystalline aggregates were found as sub-millimeter-size inclusions with a pseudomorph after coesite (?) in omphacites from a number of Sulu eclogites. In these aggregates, round or subhedral barites occur as tiny inclusions in either K-feldspar or quartz. Energy dispersive spectroscopy (EDS) analyses show that these barites have (1) 33.86%–41.12% SO₃, 0%–34.65% SrO, and 24.12%–63.55% BaO, (2) seemingly negative linear correlations between SrO and BaO, indicating that they are ideal solid solutions of barite (BaSO₄) and celestite (SrSO₄), and (3) highly variable Sr/Ba molar ratios ranging from 0 to 2.1. Presence of barites in the Sulu ecologites not only indicates oxidation of the subducting continental crust, but also very limited and restricted fluids presented during exhumation of the Sulu UHP eclogites.