Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5)
The Dergaon fall represents a shock-melted H4-5 (S5) ordinary chondrite which includes at least ten textural varieties of chondrules and belongs to the high chondrule-matrix ratio type. Our study reveals that the chondrules are of diverse mineralogy with variable olivine-pyroxene ratios (Type II), i...
Main Authors: | , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
Elsevier
2017-05-01
|
Series: | Geoscience Frontiers |
Subjects: | |
Online Access: | http://www.sciencedirect.com/science/article/pii/S1674987116300160 |
id |
doaj-c00fb14780aa44e7a5f38bc179c63e95 |
---|---|
record_format |
Article |
spelling |
doaj-c00fb14780aa44e7a5f38bc179c63e952020-11-24T22:24:23ZengElsevierGeoscience Frontiers1674-98712017-05-018341342310.1016/j.gsf.2016.02.005Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5)D. Ray0S. Ghosh1T.K. Goswami2M.J. Jobin3PLANEX, Physical Research Laboratory, Ahmedabad 380 009, IndiaPLANEX, Physical Research Laboratory, Ahmedabad 380 009, IndiaDepartment of Applied Geology, Dibrugarh University, Assam, IndiaDepartment of Applied Geology, Pondicherry University, IndiaThe Dergaon fall represents a shock-melted H4-5 (S5) ordinary chondrite which includes at least ten textural varieties of chondrules and belongs to the high chondrule-matrix ratio type. Our study reveals that the chondrules are of diverse mineralogy with variable olivine-pyroxene ratios (Type II), igneous melt textures developed under variable cooling rates and formed through melt fractionations from two different melt reservoirs. Based on the experimental analogues, mineralogical associations and phase compositions, it is suggested that the Dergaon chondrules reflect two contrasting environments: a hot, dust-enriched and highly oxidized nebular environment through melting, without significant evaporation, and an arrested reducing environment concomitant with major evaporation loss of alkali and highly volatile trace elements. Coexistence of chlorapatite and merrillite suggests formation of the Dergaon matrix in an acidic accretionary environment. Textural integration and chemical homogenization occurred at ∼1 atmospheric pressure and a mean temperature of 765 °C mark the radiogenic thermal event. Equilibrated shock features (olivine mosaicism, diaplectic plagioclase, polycrystalline troilite) due to an impact-induced thermal event reflect a shock pressure >45 GPa and temperature of 600 °C. By contrast, the local disequilibrium shock features (silicate melt veins comprising of olivine crystallites, troilite melt veins and metal droplets) correspond to a shock pressure up to 75 GPa and temperature >950 °C.http://www.sciencedirect.com/science/article/pii/S1674987116300160Dergaon chondriteChondruleThermal metamorphismShock metamorphism |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
D. Ray S. Ghosh T.K. Goswami M.J. Jobin |
spellingShingle |
D. Ray S. Ghosh T.K. Goswami M.J. Jobin Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5) Geoscience Frontiers Dergaon chondrite Chondrule Thermal metamorphism Shock metamorphism |
author_facet |
D. Ray S. Ghosh T.K. Goswami M.J. Jobin |
author_sort |
D. Ray |
title |
Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5) |
title_short |
Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5) |
title_full |
Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5) |
title_fullStr |
Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5) |
title_full_unstemmed |
Insights into chondrule formation process and shock-thermal history of the Dergaon chondrite (H4-5) |
title_sort |
insights into chondrule formation process and shock-thermal history of the dergaon chondrite (h4-5) |
publisher |
Elsevier |
series |
Geoscience Frontiers |
issn |
1674-9871 |
publishDate |
2017-05-01 |
description |
The Dergaon fall represents a shock-melted H4-5 (S5) ordinary chondrite which includes at least ten textural varieties of chondrules and belongs to the high chondrule-matrix ratio type. Our study reveals that the chondrules are of diverse mineralogy with variable olivine-pyroxene ratios (Type II), igneous melt textures developed under variable cooling rates and formed through melt fractionations from two different melt reservoirs. Based on the experimental analogues, mineralogical associations and phase compositions, it is suggested that the Dergaon chondrules reflect two contrasting environments: a hot, dust-enriched and highly oxidized nebular environment through melting, without significant evaporation, and an arrested reducing environment concomitant with major evaporation loss of alkali and highly volatile trace elements. Coexistence of chlorapatite and merrillite suggests formation of the Dergaon matrix in an acidic accretionary environment. Textural integration and chemical homogenization occurred at ∼1 atmospheric pressure and a mean temperature of 765 °C mark the radiogenic thermal event. Equilibrated shock features (olivine mosaicism, diaplectic plagioclase, polycrystalline troilite) due to an impact-induced thermal event reflect a shock pressure >45 GPa and temperature of 600 °C. By contrast, the local disequilibrium shock features (silicate melt veins comprising of olivine crystallites, troilite melt veins and metal droplets) correspond to a shock pressure up to 75 GPa and temperature >950 °C. |
topic |
Dergaon chondrite Chondrule Thermal metamorphism Shock metamorphism |
url |
http://www.sciencedirect.com/science/article/pii/S1674987116300160 |
work_keys_str_mv |
AT dray insightsintochondruleformationprocessandshockthermalhistoryofthedergaonchondriteh45 AT sghosh insightsintochondruleformationprocessandshockthermalhistoryofthedergaonchondriteh45 AT tkgoswami insightsintochondruleformationprocessandshockthermalhistoryofthedergaonchondriteh45 AT mjjobin insightsintochondruleformationprocessandshockthermalhistoryofthedergaonchondriteh45 |
_version_ |
1725761628629106688 |