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Shergottite Northwest Africa 6963: A Pyroxene‐Cumulate Martian Gabbro
No full textNorthwest Africa (NWA) 6963 was found in Guelmim‐Es‐Semara, Morocco, and based on its bulk chemistry and oxygen isotopes, it was classified as a Martian meteorite. On the basis of a preliminary study of the textures and crystal sizes, it was resubclassified as a gabbroic shergottite because of the similarity with terrestrial and lunar gabbros. However, the previous work was not a quantitative investigation of NWA 6963; to supplement the original resubclassification and enable full comparison between this and other Martian samples; here we investigate the mineralogy, petrology, geochemistry, quantitative textural analyses, and spectral properties of gabbroic shergottite NWA 6963 to constrain its petrogenesis, including the depth of emplacement (i.e., base of a flow versus crustal intrusion). NWA 6963 is an enriched shergottite with similar mineralogy to the basaltic shergottites but importantly does not contain any fine‐grained mesostasis. Consistent with the mineralogy, the reflectance (visible/near‐infrared and thermal infrared) spectrum of powdered NWA 6963 is similar to other shergottites because they are all dominated by pyroxene, but its reflectance is distinct in terms of albedo and spectral contrast due to its gabbroic texture. NWA 6963 represents a partial cumulate gabbro that is associated with the basaltic shergottites. Therefore, NWA 6963 could represent a hypabyssal intrusive feeder dike system for the basaltic shergottites that erupted on the surface
Shergottite Northwest Africa 6963: A Pyroxene-Cumulate Martian Gabbro
No full textNorthwest Africa (NWA) 6963 was found in Guelmim-Es-Semara, Morocco, and based on its bulk chemistry and oxygen isotopes, it was classified as a Martian meteorite. On the basis of a preliminary study of the textures and crystal sizes, it was resubclassified as a gabbroic shergottite because of the similarity with terrestrial and lunar gabbros. However, the previous work was not a quantitative investigation of NWA 6963; to supplement the original resubclassification and enable full comparison between this and other Martian samples; here we investigate the mineralogy, petrology, geochemistry, quantitative textural analyses, and spectral properties of gabbroic shergottite NWA 6963 to constrain its petrogenesis, including the depth of emplacement (i.e., base of a flow versus crustal intrusion). NWA 6963 is an enriched shergottite with similar mineralogy to the basaltic shergottites but importantly does not contain any fine-grained mesostasis. Consistent with the mineralogy, the reflectance (visible/near-infrared and thermal infrared) spectrum of powdered NWA 6963 is similar to other shergottites because they are all dominated by pyroxene, but its reflectance is distinct in terms of albedo and spectral contrast due to its gabbroic texture. NWA 6963 represents a partial cumulate gabbro that is associated with the basaltic shergottites. Therefore, NWA 6963 could represent a hypabyssal intrusive feeder dike system for the basaltic shergottites that erupted on the surface
Identification of ambiguities in the 1994 chronic fatigue syndrome research case definition and recommendations for resolution
No full textThis is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.
The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1472-6963/3/25
Crystallization History of Gabbroic Shergottite NWA 6963 as Revealed by Pyroxene Zoning
No full textNorthwest Africa 6963 (NWA 6963) is an intriguing new coarse grained, gabbroic Martian meteorite that further extends our sample collection both compositionally and texturally. Basaltic shergottites offer insight to volcanic igneous processes on the Martian surface and can be used to predict subsurface conditions. Gabbroic shergottite NWA 6963 provides direct petrologic evidence of intrusive igneous conditions within the Martian crust that extrusive meteorite samples cannot match. NWA 6963 is composed of coarse grained clinopyroxenes and maskelynite with sub-ophitic textures supporting its intrusive origin. Zoning textures in clinopyroxenes, augite and pigeonite, are analyzed to determine the crystallization history of NWA 6963. Compositional zoning profiles reveal pyroxenes with augite or pigeonite cores mantled by Fe-rich pigeonite rims. In NWA 6963 the pyroxenes cores are in equilibrium with one another, but cores are not in equilibrium with respective Fe-rich pigeonite rims in the same grain. This study suggests reasons for complex pyroxene textures and compositions observed in NWA 6963 are due to magma undercooling and possibly volatile expulsion during two distinct stages of crystallization history
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Crystallization history of gabbroic shergottite NWA 6963 as revealed by pyroxene zoning
No full textNorthWest Africa (NWA) 6963 is an intriguing new coarse grained Martian meteorite that further extends our sample collection both compositionally and texturally. It was originally documented as a basaltic shergottite because the pyroxene compositions and modal abundances are similar to Shergotty. However, recent work reclassified NWA 6963 as an intrusive, gabbroic Martian meteorite because of the large oriented pyroxene crystals. This investigation will focus on NWA 6963 pyroxene zoning profiles and interpreting igneous processes related to its crystallization history.
Compositional zoning of pyroxene crystals in basaltic shergottites have previously been interpreted for petrology and degrees of undercooling. In addition, cooling rates of Martian magmas have been determined experimentally to constrain volcanic processes based on both pyroxene and olivine zoning. These studies interpret crystallization histories of basaltic shergottites and provide valuble insight of volcanic flows on Mars. However, igneous conditions below the Martian surface can now be constrained with instrusive shergottite NWA 6963. The crystallization history of a gabbroic shergottite is expected to differ from basaltic Martian meteorites due to the nature of instrusive and extrusive igneous conditions. Determining rates of cooling from pyroxene zoning will further constrain the petrogenetic history of NWA 6963. This will provide new information on the nature of instrusive igneous processes within the shallow Martian subsurface
Constraints on the petrologic history of gabbroic shergottite Northwest Africa 6963 from pyroxene zoning profiles and electron backscattered diffraction
No full textNorthwest Africa 6963 (NWA 6963) is a coarse-grained, gabbroic Martian meteorite that further extends our Martian sample collection, both compositionally and texturally. Gabbroic shergottite NWA 6963 provides direct petrologic evidence of intrusive igneous conditions within the Martian crust. Here, we analyzed geochemical zoning profiles and microstructural-crystallographic information from electron backscattered diffraction of augite and pigeonite to constrain the crystallization history of NWA 6963. Compositional zoning profiles reveal pyroxenes with augite or pigeonite cores mantled by Fe-rich pigeonite rims. Our results suggest complex pyroxene textures and zoning profiles observed in pyroxenes in NWA 6963 are due to pyroxene accumulation from a crystallizing magma in a large intrusive environment (sill or magma chamber); however, without geologic context or companion samples, it is currently impossible to rule out accumulation at the base of a very large (>>100 m) differentiated flow
Applicability of a previously validated readmission predictive index in medical patients in Singapore: a retrospective study
No full text10.1186/1472-6963-13-366BMC Health Services Research13136
Estimated time spent on preventive services by primary care physicians
No full text10.1186/1472-6963-8-245BMC Health Services Research8
Impact of data source and time reference of functional status on hospital mortality prediction
No full text10.1186/1472-6963-12-115BMC Health Services Research12111
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