LINK<\/strong><\/a><\/p>\n\n\n\n“Two alternative petrogenetic models, plagioclase flotation and serial magmatism have been proposed to explain the origin of the lunar anorthositic crust, covering ~80% of the lunar highland. In this study, we re-examine the possible relict igneous texture present in an inferred lunar highland breccia clast (area ~1 mm2) in the Dhofar 081 meteorite. Our new petrographic and in-situ mineral microprobe chemical data on this clast show this coarse grained (average grain size ~0.5 mm) clast preserves relict igneous texture where subhedral, prismatic low-Ca pyroxene has intergrown with anhedral anorthitic plagioclase, suggesting its eutectic crystallization from its parent silicate magma. Absence of maskelynite and similarity of Na, K contents of plagioclase with the FAN assemblages negate the possibility of crystallization of the studied relict clast from an impact melt. The mineral-chemical data of Dhofar 081 suggest it is FAN (Ferroan anorthosite) in composition (after Warren in Annu. Rev. Earth Planet. Sci. 13:201\u2013240, 1985). Hence, intergrown crystallization of minerals in the present relict igneous clasts and other reported FAN samples argues against a cumulate origin of the lunar anorthosite. The orthopyroxenes present in the unbrecciated portion of this meteoritic clast include bimodal low- and high-iron geochemical sub-groups. The application of orthopyroxene and plagioclase thermobarometry (after Gasparik in Contrib. Mineral. Petrol. 96:357\u2013370, 1987) on our new microprobe data, and also two-pyroxene thermometry (after Lindsley in Am. Mineral. 68:477\u2013493, 1983; Putirka in Rev. Mineral. Geochem. 69(1):61\u2013120, 2008) on our new microprobe data and synthesis of literature data constrain the pressure and temperature of crystallization of lunar anorthosite parent magma close to 8 kbar and 1050\u00b0C, respectively. Application of Fo\u2013An\u2013Q experimental phase diagram at high pressure (up to 20 kbar) negates the possibility of generation of lunar anorthosite from a lherzolite source, the parent magma of these anorthosites probably lie on or close to Fo\u2013An join of this phase diagram close to the spinel field.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Dwijesh Ray, Saumitra Misra & David R Nelson Journal of Earth System Science, Volume 130Article number: 39 (2021)Published: 13 February 2021 LINK “Two alternative petrogenetic models, plagioclase flotation and serial magmatism have been proposed to…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[41],"tags":[706,5864,1827,2745,2235,1857],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/26177"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=26177"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/26177\/revisions"}],"predecessor-version":[{"id":26178,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/26177\/revisions\/26178"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=26177"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=26177"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=26177"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}