The formation of garnet in olivine-bearing metagabbros from the Adirondacks
dc.contributor.author | Essene, Eric J. | en_US |
dc.contributor.author | Johnson, Craig A. | en_US |
dc.date.accessioned | 2006-09-11T18:51:31Z | |
dc.date.available | 2006-09-11T18:51:31Z | |
dc.date.issued | 1982-12 | en_US |
dc.identifier.citation | Johnson, Craig A.; Essene, Eric J.; (1982). "The formation of garnet in olivine-bearing metagabbros from the Adirondacks." Contributions to Mineralogy and Petrology 81(3): 240-251. <http://hdl.handle.net/2027.42/47335> | en_US |
dc.identifier.issn | 1432-0967 | en_US |
dc.identifier.issn | 0010-7999 | en_US |
dc.identifier.uri | https://hdl.handle.net/2027.42/47335 | |
dc.description.abstract | A regional study of olivine-bearing metagabbros in the Adirondacks has permitted testing of the P(pressure)-T(temperature)-X(composition) dependence of garnet-forming reactions as well as providing additional regional metamorphic pressure data. Six phases, olivine, orthopyroxene, clinopyroxene, garnet, plagioclase and spinel, which can be related by the reactions: orthopyroxene+clinopyroxene+spinel +anorthite=garnet, and forsterite+anorthite=garnet occur together both in coronal and in equant textures indicative of equilibrium. Compositions of the respective minerals are typically Fo 25–72 , En 44–75 , En 30–44 Fs 9–23 Wo 47–49 , Pp 13–42 Alm 39–63 Gr 16–20 , An 29–49 and Sp 16–58 . When they occur in the same rock, equant and coronal garnets are homogeneous and compositionally identical suggesting that chemical equilibrium may have been attained despite coronal textures. Extrapolating reactions in the simple CMAS system to granulite temperatures and making thermodynamic corrections for solid solutions gives equilibration pressures (using the thermometry of Bohlen et al. 1980b) ranging from about 6.5 kb in the Lowlands and southern Adirondacks to 7.0–8.0 kb in the Highlands for the assemblage olivine-plagioclase-garnet. These results are consistent with inferred peak metamorphic conditions in the Adirondacks (Valley and Bohlen 1979; Bohlen and Boettcher 1981). Thus the isobaric retrograde path suggested by Whitney and McLelland (1973) and Whitney (1978) for the formation of coronal garnet in olivine metagabbros may not be required. Application of the same equilibria gives >8.7 kb for South Harris, Scotland and 0.9 kb for the Nain Complex. Disagreement of the latter value with orthopyroxeneolivine-quartz barometry (Bohlen and Boettcher 1981) suggests that the use of iron-rich rocks (olivines ≧Fa 50 ) results in errors in calculated pressures. | en_US |
dc.format.extent | 1541603 bytes | |
dc.format.extent | 3115 bytes | |
dc.format.mimetype | application/pdf | |
dc.format.mimetype | text/plain | |
dc.language.iso | en_US | |
dc.publisher | Springer-Verlag | en_US |
dc.subject.other | Geosciences | en_US |
dc.subject.other | Geology | en_US |
dc.subject.other | Mineralogy | en_US |
dc.subject.other | Mineral Resources | en_US |
dc.title | The formation of garnet in olivine-bearing metagabbros from the Adirondacks | en_US |
dc.type | Article | en_US |
dc.subject.hlbsecondlevel | Geology and Earth Sciences | en_US |
dc.subject.hlbsecondlevel | Chemistry | en_US |
dc.subject.hlbtoplevel | Science | en_US |
dc.description.peerreviewed | Peer Reviewed | en_US |
dc.contributor.affiliationum | Department of Geological Sciences, The University of Michigan, 48109, Ann Arbor, Michigan, USA; Climax Molybdenum Co., P.O. Box 961, 89820, Battle Mountain, Nevada, USA | en_US |
dc.contributor.affiliationum | Department of Geological Sciences, The University of Michigan, 48109, Ann Arbor, Michigan, USA | en_US |
dc.contributor.affiliationumcampus | Ann Arbor | en_US |
dc.description.bitstreamurl | http://deepblue.lib.umich.edu/bitstream/2027.42/47335/1/410_2004_Article_BF00371301.pdf | en_US |
dc.identifier.doi | http://dx.doi.org/10.1007/BF00371301 | en_US |
dc.identifier.source | Contributions to Mineralogy and Petrology | en_US |
dc.owningcollname | Interdisciplinary and Peer-Reviewed |
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