Metamorphic paragenesis of the Bjørkedalen peridotite, western Norway: implications of amphibole zoning

dc.contributor.advisorYoung, David J.
dc.contributor.authorPasillas, Nancy
dc.contributor.committeeMemberBirnbaum, Stuart J.
dc.contributor.committeeMemberGray, Walter
dc.date.accessioned2024-02-12T19:29:20Z
dc.date.available2024-02-12T19:29:20Z
dc.date.issued2015
dc.descriptionThis item is available only to currently enrolled UTSA students, faculty or staff. To download, navigate to Log In in the top right-hand corner of this screen, then select Log in with my UTSA ID.
dc.description.abstractThe Bjørkedalen peridotite in the Western Gneiss Region (WGR) of Norway has a mineral assemblage consisting of abundant hydrous minerals implying significant presence of water during metamorphism. Examining mineral chemistry and textural relationships in peridotite samples leads to inferences about the pressure, temperature and fluid infiltration history of the mantle. This research aims to understand the metamorphic evolution of the hydrous assemblage, the appearance of amphiboles, and the pressure-temperature implications of amphibole zoning. I seek to understand whether this zoning developed on the prograde or retrograde path, and thus whether the peridotite was entrained during subduction or subsequent exhumation. These objectives are accomplished by thermodynamic modeling of whole rock analyses using Perpl_X and comparing these equilibrium models to modal and chemical analyses of chlorite and amphibole obtained by scanning electron microscopy (SEM) and an electron microprobe analyzer (EMPA). Chronology of the WGR is well understood: subduction to peak conditions of 750?C and 3.5 GPa between 425-400 Ma followed by decompression and amphibolite facies metamorphism during near-isothermal exhumation at 750 °C, 1.5-0.5 GPa between 400-380 Ma. Our results indicate that the hydrous mineral development took place on a retrograde path. Retrograde features include chlorite growing at the expense of spinel and anthophyllite overgrowths around tremolite cores. The retrogressive P-T path that produced the mineral assemblage of the Bjørkedalen peridotite is consistent with decompression following ultrahigh pressure metamorphism and the overprint of amphibolite-facies retrogression during exhumation in the WGR.
dc.description.departmentGeosciences
dc.format.extent56 pages
dc.format.mimetypeapplication/pdf
dc.identifier.isbn9781339034669
dc.identifier.urihttps://hdl.handle.net/20.500.12588/4853
dc.languageen
dc.subjectAmphibole zoning
dc.subjectBjørkedalen
dc.subjectWestern Gneiss Region
dc.subjectWestern Norway
dc.subjectperidotite
dc.subject.classificationGeology
dc.subject.classificationPetrology
dc.subject.lcshGeology -- Norway -- Vestlandet
dc.subject.lcshMetamorphism (Geology) -- Norway -- Vestlandet
dc.subject.lcshPeridotite -- Norway -- Vestlandet
dc.subject.lcshAmphiboles -- Norway -- Vestlandet
dc.subject.lcshGneiss -- Norway -- Vestlandet
dc.titleMetamorphic paragenesis of the Bjørkedalen peridotite, western Norway: implications of amphibole zoning
dc.typeThesis
dc.type.dcmiText
dcterms.accessRightspq_closed
thesis.degree.departmentGeosciences
thesis.degree.grantorUniversity of Texas at San Antonio
thesis.degree.levelMasters
thesis.degree.nameMaster of Science

Files

Original bundle

Now showing 1 - 1 of 1
No Thumbnail Available
Name:
Pasillas_utsa_1283M_11725.pdf
Size:
3.98 MB
Format:
Adobe Portable Document Format