New observations on high‐pressure phases in a shock melt vein in the Villalbeto de la Peña meteorite: Insights into the shock behavior of diopside
Year: 2019
Type: article
Abstract: The petrology and mineralogy of shock melt veins in the L6 ordinary chondrite host of Villalbeto de la Peña, a highly shocked, L chondrite polymict breccia, have been investigated in detail using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and electron probe microanalysis. Entrained olivine, enstatite, diopside, and plagioclase are transformed into ringwoodite, low‐Ca majorite, high‐Ca majorite, and an assemblage of jadeite‐lingunite, respectively, in several shock melt veins and pockets. We have focused on the shock behavior of diopside in a particularly large shock melt vein (10 mm long and up to 4 mm wide) in order to provide additional insights into its high‐pressure polymorphic phase transformation mechanisms. We report the first evidence of diopside undergoing shock‐induced melting, and the occurrence of natural Ca‐majorite formed by solid‐state transformation from diopside. Magnesiowüstite has also been found as veins injected into diopside in the form of nanocrystalline grains that crystallized from a melt and also occurs interstitially between majorite‐pyrope grains in the melt‐vein matrix. In addition, we have observed compositional zoning in majorite‐pyrope grains in the matrix of the shock‐melt vein, which has not been described previously in any shocked meteorite. Collectively, all these different lines of evidence are suggestive of a major shock event with high cooling rates. The minimum peak shock conditions are difficult to constrain, because of the uncertainties in applying experimentally determined high‐pressure phase equilibria to complex natural systems. However, our results suggest that conditions between 16 and 28 GPa and 2000–2200 °C were reached.
DOI: 10.1111/maps.13391
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: THE RESEARCH OUTLINED IN THIS PROPOSAL IS DIRECTED TOWARDS UNDERSTANDING THE NATURE AND ORIGIN OF A VARIETY OF COMPONENTS INCHONDRITIC METEORITES IN THE CONTEXT OF EARLY SOLAR NEBULAR AND PARENT BODY EVOLUTION. THE RESEARCH SPECIFICALLY ADDRESS NASA STRATEGIC GOAL 2 TO `ADVANCE SCIENTIFIC KNOWLEDGE OF THE ORIGIN AND HISTORY OF THE SOLAR SYSTEM AND THE POTENTIAL FOR LIFE ELSEWHERE . THE GOALS OF THE RESEARCH ARE TO UNRAVEL THE COMPLEX SEQUENCE OF EVENTS THAT PRODUCED THE CHEMICALLY AND MINERALOGICALLY DIVERSE ASSEMBLAGES OBSERVED IN PRIMITIVE METEORITES. WE WILL CARRY OUT MINERALOGICAL PETROLOGIC AND ISOTOPIC STUDIES USING A VARIETY OF MICROBEAM TECHNIQUES (SEM EPMA FIB/TEM NANOSIMS AND SXRF MICROPROBE) AS WELL AS STABLE ISOTOPE TECHNIQUES IN A COLLABORATIVE EFFORT WITH SEVERAL OTHER RESEARCH GROUPS. OUR PROPOSED STUDIES ARE DIVIDED INTO FOUR SPECIFIC AREAS: 1) MINERALOGICAL AND STABLE ISOTOPIC STUDIES TO CONSTRAIN AQUEOUS ALTERATION PROCESSES IN CR CHONDRITES 2) MICROSTRUCTURAL AND STABLE ISOTOPIC STUDIES OF AMEBOID OLIVINE AGGREGATES (AOAS) AND CAIS IN CO3 CHONDRITES TO CONSTRAIN THEIR FORMATION AND THERMAL HISTORIES. 3) EPMA AND TEM STUDIES OF METASOMATIC AND METAMORPHIC EFFECTS IN REFRACTORY INCLUSIONS (AOAS AND CAIS) CO3 CHONDRITES 4) TEM AND TRACE ELEMENT STUDIES OF SULFIDES IN CM CHONDRITES TO CONSTRAIN THEIR FORMATIONAL AND THERMAL HISTORIES. FOR RESEARCH TASK 1 WEWILL ALSO EXAMINE THE MINERALOGICAL EVOLUTION OF MATRICES IN CR CHONDRITES AS INDICATORS OF PROGRESSIVE ALTERATION FOCUSING ON THE ROLE OF HYDRATED AMORPHOUS MATERIAL AS AN INDICATOR OF THE INTENSITY OF ALTERATION. THIS WORK WILL INVOLVE COORDINATED FIB/TEM IR NANOSIMS HYDROGEN AND OXYGEN ISOTOPIC ANALYSES TO CONSTRAIN THE PROGRESSIVE ALTERATION OF CR CHONDRITE MATRICES IN MORE DETAIL. WE WILL ALSO STUDY THE MECHANISMS OF HYDRATION OF SILICATE GLASS IN CHONDRULES IN CR CHONDRITES TO CONSTRAIN THE ALTERATION MECHANISM AND PROCESSES OF ELEMENTAL MASS TRANSPORT AND ELEMENTAL AND ISOTOPIC EXCHANGE. FOR RESEARCH TASK 2 WE WILL CARRY OUTCOORDINATED FIB/TEM AND NANOSIMS OXYGEN ISOTOPIC STUDIES OF THE REFRACTORY COMPONENT OF AMEBOID OLIVINE AGGREGATES AND CAIS IN CO CHONDRITES TO CONSTRAIN THEIR FORMATION AND THERMAL HISTORIES. IN PARTICULAR WE WILL FOCUS ON AOAS AND CAIS THAT SHOW EVIDENCE OF COMPLEX THERMAL HISTORIES THAT MAY BE INDICATIVE OF TRANSPORT AND INTERACTION WITH THE GAS PHASE IN DIFFERENT REGIONS OF THE SOLAR NEBULA. A COMPONENT OF THIS WORK WILL INVOLVE THE STUDY OF REFRACTORY METAL NANOPARTICLES WHICH WE HAVE RECENTLY DISCOVERED IN SITU IN AOAS IN CO3 CHONDRITES. THIS EFFORT WILL HELP CONSTRAIN THE POTENTIAL ORIGINS OF REFRACTORY METAL ALLOYS WHICH OCCUR IN OTHER TYPES OF CARBONACEOUS CHONDRITES. FOR RESEARCH TASK 3 WE WILL INVESTIGATE THE DETAILED RESPONSE OF CAIS AND AOAS IN CO3 CHONDRITES TO THERMAL METAMORPHISM AND METASOMATISM USING SEM EPMA AND FIB/TEM IN ORDER TO DEVELOP A MORE THOROUGH UNDERSTANDING OF THE INTERRELATIONSHIPS BETWEEN THESE TWO PROCESSES AND CONSTRAIN THE ROLE OF FLUIDS IN THE ALTERATION PROCESSES. FOR RESEARCH TASK 4 WE WILL PERFORM COORDINATE SEM EPMA FIB/TEM AND SXRF STUDIES OF PRISTINE SULFIDES IN CM CHONDRITES IN ORDER TO UNDERSTAND THE NEBULAR FORMATION AND SUBSEQUENT COOLING HISTORIES OF SULFIDE MINERALS. THIS WORK WILL PROVIDE CONSTRAINTS ON THE THERMAL HISTORIESOF CHONDRULES PARTICULARLY TYPE IIA CHONDRULES IN THIS TWO CHONDRITE GROUP. AS PART OF THIS EFFORT WE WILL DEVELOPMENT TECHNIQUES TO CARRY OUT HIGH SPATIAL RESOLUTION TRACE ELEMENT (CHALCOPHILE) ANALYSES ON FIB SECTIONS USING THE MODIFIED SXRF BEAM LINE AT THE ADVANCED PHOTON SOURCE ARGONNE NATIONAL LABORATORY AND THE NEW NSLS II FACILITY AT BROOKHAVEN NATIONAL LABORATORY THAT WILLCOME ON LINE IN 2015., G4371774311, G4864394673
OpenAlex ID: W2975942806