Search results for "petrology"
showing 10 items of 1516 documents
Evidence for boron incorporation into the serpentine crystal structure
2011
Serpentinite mud volcanoes from the Mariana forearc comprise B-rich mantle wedge peridotites serpentinized by slab fluids. The major component of these rocks are serpentine group minerals [Mg 3 Si 2 O 5 (OH) 4 ], showing highly variable textural and geochemical features. Micro-Raman spectroscopy reveals that the serpentine minerals are well-crystallized lizardite and chrysotile. In situ SIMS spot analyses and element mapping via ToF-SIMS show that B is evenly distributed across serpentine grains, suggesting that serpentine, both lizardite and chrysotile in different textural regions, can host significant amounts of B (up to ~200 μg/g) into its crystal structure. As such structurally bound B…
Extracting science from Mössbauer spectroscopy on Mars
2003
[1] Deployment by the Mars Exploration Rovers of backscatter Mossbauer spectrometers offers an incredible opportunity to (1) elucidate the iron mineralogies of rocks, soils, and atmospheric dust and (2) gain insight into the physical event by which the mineralogy came into existence and consequently acquire information having potential for yielding ancient planetary history relevant to broad issues including the question of life. Determining the mineralogy is done by subjecting raw data to reduction algorithms and generating products known as Mossbauer parameters, which are highly characteristic. Mixed mineralogies are treated through deconvolution. Through being able to exploit Mossbauer m…
Nickel on Mars: Constraints on meteoritic material at the surface
2006
[1] Impact craters and the discovery of meteorites on Mars indicate clearly that there is meteoritic material at the Martian surface. The Alpha Particle X-ray Spectrometers (APXS) on board the Mars Exploration Rovers measure the elemental chemistry of Martian samples, enabling an assessment of the magnitude of the meteoritic contribution. Nickel, an element that is greatly enhanced in meteoritic material relative to samples of the Martian crust, is directly detected by the APXS and is observed to be geochemically mobile at the Martian surface. Correlations between nickel and other measured elements are used to constrain the quantity of meteoritic material present in Martian soil and sedimen…
Search for magnetic minerals in Martian rocks: Overview of the Rock Abrasion Tool (RAT) magnet investigation on Spirit and Opportunity
2008
[1] The Rock Abrasion Tool (RAT) on board the Mars Exploration Rovers (MER) is a grinding tool designed to remove dust coatings and/or weathering rinds from rocks and expose fresh rock material. Four magnets of different strengths that are built into the structure of the RAT have been attracting substantial amounts of magnetic material during RAT activities from rocks throughout both rover missions. The RAT magnet experiment as performed on Spirit demonstrates the presence of a strongly ferrimagnetic phase in Gusev crater rocks, which based on Mossbauer and visible/near-infrared reflectance spectra is interpreted as magnetite. The amount of abraded rock material adhering to the magnets vari…
Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations
2011
Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclasti…
The new Athena alpha particle X-ray spectrometer for the Mars Exploration Rovers
2003
[1] The new alpha particle X-ray spectrometer (APXS) is part of the Athena payload of the two Mars Exploration Rovers (MER). The APXS sensor head is attached to the turret of the instrument deployment device (IDD) of the rover. The APXS is a very light-weight instrument for determining the major and minor elemental composition of Martian soils, rocks, and other geological materials at the MER landing sites. The sensor head has simply to be docked by the IDD on the surface of the selected sample. X-ray radiation, excited by alpha particles and X rays of the radioactive sources, is recorded by a high-resolution X-ray detector. The X-ray spectra show elements starting from sodium up to yttrium…
Athena Mars rover science investigation
2003
[1] Each Mars Exploration Rover carries an integrated suite of scientific instruments and tools called the Athena science payload. The primary objective of the Athena science investigation is to explore two sites on the Martian surface where water may once have been present, and to assess past environmental conditions at those sites and their suitability for life. The remote sensing portion of the payload uses a mast called the Pancam Mast Assembly (PMA) that provides pointing for two instruments: the Panoramic Camera (Pancam), and the Miniature Thermal Emission Spectrometer (Mini-TES). Pancam provides high-resolution, color, stereo imaging, while Mini-TES provides spectral cubes at mid-inf…
Nano-inclusion suite and high resolution micro-computed-tomography of polycrystalline diamond (framesite) from Orapa, Botswana
2011
Abstract A single polycrystalline diamond aggregate from the Orapa kimberlite (Botswana) contains a syngenetic micro- and nano-inclusion suite of magnetite, pyrrhotite, omphacite, garnet, rutile and C–O–H fluid in order of abundance. This suite of inclusions is distinctly different from those in fibrous diamonds, although the presence of sub-micrometer fluid inclusions provides evidence for a similarly important role of fluids in the genesis of polycrystalline diamond. It is the first study of polycrystalline diamond by High resolution μ-CT (Computed Tomography) reaching a resolution of 1.3 μm using polychromatic X-rays. Combined with Focused Ion Beam assisted Transmission Electron Microsco…
A Raman calibration for the quantification of SO42-groups dissolved in silicate glasses: Application to natural melt inclusions
2017
Sulfur is an important volatile element involved in magmatic systems. Its quantification in silicate glasses relies on state-of-the-art techniques such as electronprobe microanalyses (EPMA) or X-ray absorption spectroscopy but is often complicated by the fact that S dissolved in silicate glasses can adopt several oxidation states (S6+for sulfates or S2-for sulfides). In the present work, we use micro-Raman spectroscopy on a series of silicate glasses to quantify the S content. The database is constituted by 47 silicate glasses of various compositions (natural and synthetic) with S content ranging from 1179 to 13 180 ppm. Most of the investigated glasses have been synthesized at high pressur…
The behaviour of zirconium and hafnium during water-rock interaction
2018
Abstract Zr and Hf are two elements with same ionic charge and similar ionic size at a given coordination number. Despite the Zr/Hf ratio is quite constant in meteorites and lithospheric rocks, in natural waters can be either higher or lower compared to values of interacting minerals and rocks. Here, we reanalyze very recent published and present new data on continental and brine waters indicating that the Zr and Hf behavior is dependent on the properties of the authigenic phases formed during the water-rock interaction process. Our results show that water pH in the range between 1 and 9 and water ionic strength in the range between 0.001 and 4 mol kg−1 are responsible for the change of the…