Garnet-fassaite calc-silicate nodule from La soufriire. st. vincent
نویسنده
چکیده
The mineralogy of an unusual calc-silicate nodule brought to the surfaoe by the 1902 eruption of La Soufriere volcano on St. Vincent (Lesser Antilles arc) is described. It consists of the crystalloblastic mineral assemblage fassaite pyroxene + grandite garnet + wollastonite + anorthite t calcite. The pyroxene is more aluminous (Al2O3 : 19.66 weight percent) than any previously described from terrestrial rocks, with about 45 mole percent Ca-Al Tschermak's molecule, 37 mole percent diopside, and 15 mole percent Ca-Fe3* Tschermak's molecule in solid solution. Unit-cell data have been calculated on the basis of X-ray powder diflractometry data for the fassaite (a:9.104, D: 8.828, c:5.2MA, F: 106.95.; V:426.49A3) and the grandite (grossularrr-andraditerr; a: ll.905A V: 1687Ai). We infer a paragenesis related to skarn-type metamorphism of calcareous sediment.
منابع مشابه
مطالعه ژئوشیمی مجموعه کانیایی گارنت-وزوویانیت-ولاستونیت-پیروکسن در اسکارنهای حوش، غرب تفت (استان یزد)
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