Basanite
From Free net encyclopedia
Basanite is an igneous, volcanic (extrusive) rock with aphanitic to porphyritic texture. Mineral assembly is usually abundant feldspathoids and plagioclase, and lesser alkali feldspar. Pyroxenes (clinopyroxenes) and olivines are common as phenocrysts and in the matrix. The clinopyoxenes contain significantly greater titanium, aluminium and sodium than those in typical tholeiitic basalts. Quartz is absent. Chemically basanites along with nephelinites are low in silica (42 to 45% SiO2) and high in alkalis (3 to 5.5% Na2O and K2O).
Basanites occur early in the development of oceanic basalt provinces. They are reported from the Hawaiian and the Comoro Island hotspot volcanism.[1]
Basanite is also used to refer to a black flinty jasper found in several New England states of the U. S. A. It is also informally known as lydite and touchstone. It has been used to test for the purity of precious metal alloys.
References
- Blatt, Harvey and Robert J. Tracy (1996) Petrology, 2nd ed., W. H. Freeman ISBN 0-7167-2438-3
- Buchwaldt, Robert (2003) Geochemistry and Petrology of a Miocene Trachyte-Basanite Suite from Mt. Tsaratanana, Northern Madagascar, Abstract.
- Mindat dataTemplate:Mineral-stub