Title: INTERGROWTH AND STRUCTURAL RELATION BETWEEN PYROXENE AND AMPHIBOLE
Abstract:Studies on the intergrowth and the structural relation between pyroxene and amphibole are summerized.Morphorogical intergrowth of amphibole in pyroxene has been discribed by many investigators from ig...Studies on the intergrowth and the structural relation between pyroxene and amphibole are summerized.Morphorogical intergrowth of amphibole in pyroxene has been discribed by many investigators from igneous and metamorphic rocks. Clinoamphibole overgrows on clinopyroxen e having a common b-axis to that of the pyroxene. In this case, a-and c-axes of clinoamphibole and pyroxene, respectively, are nearly or exactly parallel to each other, when the crystallographic axes of clinoamphibole and clinopyroxene are chosen in such a way that the space groups of clinoamphibole and clinopyroxene are I2/m and C2/c, respectively. Clinoamphibole structure (I2/m) is related to clinopyroxene structure (C2/c) by a displacement of I/2 (a+c) along (010) plane.Oxyhornblende are occasionally made up of two different phases, clinoa mphibole and clinopyroxene arrenged as lamellae parallel to (010) in submicrodomains. The structural relationship between clinoamphibole and clinopyroxene as above is comfirmed in this cases.Experimental studies on the thermal change of Ca-amphibole concluded that Caamphibole transforms into oxyhornblende composed of clinoamphibole and clinopyroxene phases.Amphibole lamellae have been observed in pyroxenes from basic plutonic rocks and peridotite. A kind of planar defects parallel to (010) in clinopyroxene, related to the formation of clinoamphibole lamellae, are found. From the chemical characteristics and textural relation, these amphibole lamellae are considered to have been formed by exsolution from pyroxene. A possibility of finite solid solution between amphibole and pyroxen is pointed out.Read More