45th Lunar and Planetary Science Conference (2014) 1620.pdf EVIDENCE FOR MAGMATIC-HYDROTHERMAL ACTIVITY ON MARS FROM Cl-RICH SCAPOLITE IN NAKHLA. J. Filiberto1, C.A. Goodrich2, A.H. Treiman3, J. Gross4, and P.A. Giesting1, 1Southern Illinois University, Geology Dept, Carbondale, IL 62901 USA,
[email protected], 2Planetary Science Institute, Tucson AZ 85719 USA. 3Lunar and Planetary Institute, Houston, TX 77058 USA, 4American Museum of Natural History, New York, NY USA. Introduction: Scapolite is a common terrestrial The melt inclusion containing the Cl-scapolite (Fig. hydrothermal, metamorphic, and metasomatic mineral 1) is dominated by high-Ca pyroxene, K-feldspar and which forms by the reaction of plagioclase and a Cl- or K-rich glass, with minor chromite, Fe-sulfides, Fe-Ti CO2-rich fluid [1-3]. It is less common as a primary oxides, and alteration material [9]. The occurrence of igneous phase, but has been reported as megacrysts, the scapolite appears to be texturally equivalent to the phenocrysts, and oikocrysts in alkali-rich basaltic K-feldspar or the glass (i.e., interstitial to the pyrox- magmas [4-6]. Based on reflectance spectra, scapolite enes), and may therefore be replacing, or contempora- has also been suggested to exist on the surface of Mars neous with, one of these phases. It contains ~3.9 wt.% as a possible alteration mineral [7]. Cl, and has the formula (Na2.8Ca0.7K0.3)3.9(Si8.3Al3.7)12ClO24. Scapolite has three main end member composi- It is almost pure end-member marialite with little tions: marialite (Na4Al3Si9O24Cl), meionite meionite component (Fig. 2).