Sulphate Efflorescent Minerals from the El Jaroso Ravine, Sierra Almagrera, Spain—A Scanning Electron Microscopic and Infrared Spectroscopic Study

Abstract

Near infrared (NIR) spectroscopy is a technique that can be utilised to analyse minerals remotely through a fi bre-optic cable.A suite of sulphate effl orescent minerals from the El Jaroso ravine, Sierra Almagrera, Spain have been analysed by ultraviolet, visible, NIR and mid infrared (IR) spectroscopy. Such a suite of minerals may be used to model the types of mineral deposits on Mars. The minerals were analysed by scanning electron microscopy and X-ray microanalysis (EDX) before spectroscopic analysis. Halotrichite was observed and the EDX analyses showed the mineral to be a mixture of heinrichite and pickingerite. The NIR spectrum of the efl orescencia sample showed the sulphate deposit to be composed of a mixture of jarosite and halotrichites. The 7400 to 6400 cm -1 (1351 to 1562 nm) NIR spectral region of the effl orescent sulphate minerals can be used to characterise the various sulphate deposits. The detection of a band at 8338 cm -1 (1199 nm) reveals the presence of ferrous iron in jarosite which is unusual for the jarosite minerals. This can be caused by ferric iron reduction by thermophilic iron-oxidising bacteria. Mid IR spectra showed the characteristic OH stretching bands of the jarosites and the effl orescent mixtures. The position of water stretching vibrations at 2900 cm -1 and lower shows strong hydrogen bonding as is also evidenced by water bending modes at around 1682 cm -1 .

Characterisation of the Copper Arsenate Mineral Strashimirite, Cu8(AsO4)4(OH)4·4H2O, by near Infrared Spectroscopy

“…the splitting of both 2 e and 2 t states is the effect of site distortion for the cu 2+ ion that occupies Jahn-teller sites in many copper complexes. [28][29][30][31][32] for cu 2+ the number of bands observable is four and three in rhombic and tetragonal fields, respectively. the energies of the three bands in tetragonal field are related to 2 B 1 ® 2 a 1 , 2 B 1 ® 2 B 2 and 2 B 1 ® 2 e transitions.…”

“…[18][19][20][21][22][23][24][25] frost et al extended this research to study a range of diagenetically related mineral systems. [26][27][28][29][30][31][32][33][34][35] In this research, we are applying nIr spectroscopy to the study of the arsenate minerals from two different origins, namely strashimirite.…”

The Raman Laser Spectrometer for the ExoMars Rover Mission to Mars

“…After this discovery, potential Mars analog sites on Earth, in which jarosite is produced by different mineralogenesis processes, have become the subject of great interest (Frost et al, 2006;Edwards et al, 2007;Sobrón et al, 2009;Rull et al, 2014). Among those, the Jaroso Ravine (Almería, SE Spain), the world type locality of jarosite, and the Rio Tinto site (Huelva, SW Spain), where a wide range of hydrated sulfates can be found (Frost et al, 2005;Sobrón et al, 2009;FIG.…”

“…A wide range of Raman analyses were also performed in the Jaroso Ravine (Frost et al, 2005(Frost et al, , 2006(Frost et al, , 2007Venegas, 2014), several of them in combination with Mossbauer FIG. 26.…”

Laboratory Raman and VNIR spectroscopic studies of jarosite and other secondary mineral mixtures relevant to Mars

“…[24] However, some VNIR spectra acquired by CRISM exhibit enigmatic "doublet" spectral features with two absorption bands at~2,210 and~2,270 nm, and their band strengths vary independently, implying at least two phases are present, [25] including pure sulfates or their mixtures (structurally similar to gypsum and jarosite), [26] mixture of Fe-OH-bearing mineral (jarosite or Fe/Mg smectite) and Al-OH-bearing phase (e.g., alunite, montmorillonite, kaolinite, or halloysite), [26][27][28][29][30] and poorly crystalline Al ferric clays and/or sulfate mixtures arising from acid leaching. [26,28,31] Raman spectroscopy is a powerful tool for precise discrimination of the igneous and secondary mineral phases for laboratory, terrestrial studies, and Mars in situ explorations, [32][33][34][35][36][37][38][39][40][41] which has been applied to identify igneous (e.g., alkali feldspar) and secondary (e.g., jarosite) minerals in Martian meteorite (e.g., Miller Range 03346,168, [37][38][39] Roberts Massif 04262, [40] and Yamato-00593/794 [41] ) and terrestrial mixtures (such as the sulfate efflorescent minerals from Jaroso, Sierra [35,36] ). Due to the excellent performance in phase identifications and mineral chemistry analyses of Raman spectroscopy, three Raman payloads including Raman Laser Spectrometer, [42,43] SuperCam, [44,45] and Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals [45][46][47] have been selected in ExoMars and Mars 2020 missions, with the primary science goals of identifying fine-scale precise miner...…”