An experimental study of glaucophanic amphiboles in the system Na2O-MgO-Al2O3-SiO2-SiF4 (NMASF): some implications for glaucophane stability in natural and synthetic systems at high temperatures and pressures

Article Abstract:

A study was conducted to examine the phase relations of glaucophanic amphiboles. The synthetic system Na2O-MgO-Al2O3-SiO2-SiF4 (NMASF) was applied using the bulk composition of fluor-glaucophane, Na2Mg3Al2Si8O22F2 (NMASH). NMASH exhibited analogous phase relations with NMASF because SiF4 assumed the role of water as the fluid component. Results show that glacouphane stoichiometry approach in natural systems indicate preference for high water activites and high pressures.

Analysis, Fluorine compounds

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Exsolution of Ca-amphibole from glaucophane and the miscibility gap between sodic and calcic amphiboles

Article Abstract:

The exsolution microstructures of Ca-rich amphibole and glaucophane from two Vermont localities are characterized. Transmission and analytical electron microscopy results show that Ca-rich glaucophanes contain abundant fine-scale lamellae of Ca-rich amphibole, and these lamellae are either winchite or actinolite. Samples from Eclogite Brook exhibit the compositional variables associated with miscibility gap between sodic and calcic amphiboles.

Vermont, Natural history

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Experimental Na-K distribution between amphiboles and aqueous chloride solutions, and a mixing model along the richterite - K-richterite join

Article Abstract:

The equilibrium and distribution coefficients for Na and K between Na- and K-richterite and 1 to 2n chloridic aqueous fluids in the Na-K-Ca-Mg-Si-O-H-Cl chemical system is studied. Results show that Na-K distribution coefficients between fluids and amphiboles of the richterite K-richterite join is near unity at 700 and 800 degrees Centigrade at 200 MPa. Na-K distributions at lower temperatures are also determined.

Potassium (Chemical element), Sodium, Sodium (Chemical element), Potassium

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