Igneous and shock processes affecting chassignite amphibole evaluated using chlorine/water partitioning and hydrogen isotopes
Amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma, but also shock and postshock processes. We have analyzed amphibole and other phases from NWA 2737 melt inclusions, and we evaluate these data along with published val...
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| Published in | Meteoritics & planetary science Vol. 50; no. 3; pp. 433 - 460 |
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| Main Authors | , , , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
Hoboken
Blackwell Publishing Ltd
01.03.2015
Wiley Subscription Services, Inc |
| Subjects | |
| Online Access | Get full text |
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| Summary: | Amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma, but also shock and postshock processes. We have analyzed amphibole and other phases from NWA 2737 melt inclusions, and we evaluate these data along with published values to constrain the crystallization Cl and H2O content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains. Using a model for the Cl/OH exchange between amphibole and melt, we estimate primary crystallization OH contents of chassignite amphiboles. SIMS analysis shows that amphibole from NWA 2737 currently has 0.15 wt% H2O. It has lost ~0.6 wt% H2O from an initial 0.7–0.8 wt% H2O due to intense shock. Chassigny amphibole had on average 0.3–0.4 wt% H2O and suffered little net loss of H2O due to shock. NWA 2737 amphibole has δD ≈ +3700‰; it absorbed Martian atmosphere‐derived heavy H in the aftermath of shock. Chassigny amphibole, with δD ≤ +1900‰, incorporated less heavy H. Low H2O/Cl ratios are inferred for the primitive chassignite magma, which had significant effects on melting and crystallization. Volatiles released by the degassing of Martian magma were more Cl‐rich than on Earth, resulting in the high Cl content of Martian surface materials. |
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| Bibliography: | istex:41DC739CA88DBA41344075EB5487C3B4CBCED097 ark:/67375/WNG-0LNQFZ4N-H STFC - No. ST/I001964/1 Table S1a: Glass compositions by EMP for melt inclusion 1 in NWA 2737 (Fig. a) with totals between 97 and 100%. Table S1b: Glass compositions by EMP from melt inclusions in NWA 2737 with totals between 95 and 100.5% not in Table S2a. Italicized analyses have dubious Cl content and are not used in the Cl average (see text). Table S2a: 24-anion normalized formulas for amphibole from Chassigny. H2O content from Watson et al. (). Fe3+/∑Fe from Monkawa et al. (). Data sources: F: Floran et al. (). J: Johnson et al. (). V: Varela et al. (). M: Monkawa et al. (). N: Nekvasil et al. (). Table S2b: 24-anion normalized formulas for amphibole from Chassigny. H2O content from McCubbin et al. (). Fe3+/∑Fe from Monkawa et al. (). Data sources: F: Floran et al. (). J: Johnson et al. (). V: Varela et al. (). M: Monkawa et al. (). N: Nekvasil et al. (). Mc: McCubbin et al. (). Table S2c: 24-anion normalized formulas for amphibole from NWA 2737 with the minimum possible Fe3+/∑Fe. This implies that there are no vacancies on the A site (increasing Fe3+/∑Fe beyond these minima would result in formulas with vacancies). Data sources: Treiman: Treiman et al. (). He: He et al. (). Table S3: Averages over published data for thermobarometry. Sources for Chassigny: Floran et al. (), Johnson et al. (), Varela et al. (), Monkawa et al. (), Nekvasil et al. (), McCubbin et al. (). Sources for NWA 2737: Treiman et al. (), He et al. (). ArticleID:MAPS12430 NASA MFR - No. #NNX13AG35 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 1086-9379 1945-5100 |
| DOI: | 10.1111/maps.12430 |