{"product_id":"21002-63-nwa-possible-achondrite-meteorite-porphyritic-basalt-in-study-2441-g","title":"21002-63 - NWA Possible Achondrite Meteorite Porphyritic Basalt. In study. 244.1 g","description":"\u003cp\u003e\u003cstrong\u003ePetrographic description\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003eUnder petrographic microscope, the sample is a fine-grained volcanic rock with olivine and pyroxene euhedral phenocrysts, surrounded by fine-grained matrix (Figs. 2 and 3). \u003cstrong\u003eOlivine shows a thin rim (Figs. 2 and 3) of iddingsite (reddish border).\u003c\/strong\u003e The rock matrix is formed by tabular euhedral plagioclase and anhedral pyroxene crystals and, in a minor amount, by ilmenite grains.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003eTabular plagioclase crystals display certain orientation, suggesting flow during magma crystallization. Opaque minerals are Fe-Ti oxides, mainly ilmenite.\u003cbr\u003eOlivine has 0.5-1.3 mm μm in size whereas pyroxene varies from 200 to 400 μm. In the matrix, plagioclase, pyroxene and ilmenite microcrysts have a crystal size in the range of 50-120 μm. The percentage in the sample of olivine, pyroxene and plagioclase is respectively 12, 10 and 40%.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003eThe texture is porphyritic, glomeroporphyritic and trachytic.\u003c\/p\u003e\n\u003cp\u003eFigure 4 shows olivine and pyroxene phenocrysts surrounded by plagioclase and pyroxene microcrysts. Olivine and pyroxene are quite similar under the petrography and electronic microscope images. The main difference between them is the formation of iddingsite rim in olivine grains. Alteration processes develop the rim of the sample. Chemical zonations are not appreciable in the crystals.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003eFigure 5 shows the EDS analyses and indicates that pyroxene is augte, with Ca = 0.78 apfu (atoms per formula unit), proportion of magnesium Mg# = 0.83, and low aluminum (Al = 0.22 apfu). Olivine is magnesium rich (Fo = 0.72) and plagioclase corresponds to labradorite (XAn= 0.56).\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003cstrong\u003eThe rock is porphyritic basalt\u003c\/strong\u003e (Le Maître et al., 2005). Possible achondrite meteorite.\u003c\/p\u003e\n\u003cp\u003eMineralogy and textural properties of samples were studied on (30m-thick) polished thin sections using transmitted and reflected light microscopy at LPA (UA) and UGR.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003cstrong\u003ePhotomicrographs were performed by using:\u003c\/strong\u003e\u003cbr\u003eo Petrographic microscope: ZEISS Assioskop (LPA-UA).\u003cbr\u003eo Digital camera: USB UI-1490SE\u003cbr\u003eo Image capture Software: uEye Cockpit (IDS).\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003eSamples (polished thin-sections) also were studied under scanning electron microscope (Research Technical Services – UA). Minerals were located and identified using BSE mode on Hitachi S3000N SEM coupled with an X-ray detector Bruker XFlash 3001 for microanalysis (EDS) and mapping.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003eSemi-quantitative EDS X-ray microanalysis was performed using EDS spot analysis with acquisition time 60s and maximum process time to achieve best resolution of peaks in spectra.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003cstrong\u003eANNEX II. REFERENCES\u003c\/strong\u003e\u003cbr\u003eLe Maître, R.W. (Editor), Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., Bateman, P., Bellieni, G., Dudek, A., Efremova, S., Keller, J., Lameyre, J., Sabine, P.A., Schmid, R., Sørensen, H. \u0026amp; Woolley, A.R. 2005. Igneous Rocks: A Classification and Glossary of Terms: Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks. Cambridge University Press. Second Edition, revised, 236 p. Cambridge, UK.\u003c\/p\u003e","brand":"Jurassic Dreams","offers":[{"title":"Default Title","offer_id":58802260082991,"sku":"zbp1794156350212","price":154.91,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0986\/3213\/9055\/files\/21002-63---nwa-possible-achondrite-meteorite-porphyritic-basalt-in-study-2441-g_1.jpg?v=1794156355","url":"https:\/\/proseamfit.shop\/products\/21002-63-nwa-possible-achondrite-meteorite-porphyritic-basalt-in-study-2441-g","provider":"My Store","version":"1.0","type":"link"}