Fluid flow during Barrovian metamorphism, Stonehaven, Scotland [electronic resource]

9780496725441

2004

1 online resource (192 p.)

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A petrographic, bulk chemical, and stable isotopic study was conducted in the Dalradian metasediments north of Stonehaven, Scotland. The study was carried out to (1) determine the sources and timing of metamorphic and post metamorphic fluid flow events, and to (2) investigate the effects of metamorphic fluid flow on the chemical, mineralogical, and stable isotopic systematics of these rocks. Multiple vein sets were classified for chemical and isotopic analysis based on structural relationships and petrographic observations. Samples of protolith, vein alteration selvage, and vein material from metamorphic quartz veins were taken along a ∼1.7 km traverse extending north from the Highland Boundary Fault (HBF), a major tectonic boundary with an embedded ophiolite complex, through the biotite, garnet, chloritoid, and staurolite zones. Textural and mineralogical observations show that two vein sets are distinguished by abundant growth of plagioclase and metamorphic index minerals, including biotite, garnet, chloritoid, and staurolite, within vein selvages. Major element, trace element, and REE abundances determined from bulk chemical data (44 samples) show systematic variation on a regional scale. These variations are indicative of fluid flow-induced mass transfer during regional metamorphism. Increase in Na/Zr and Ca/Zr is coupled with K/Zr decrease relative to the protolith composition in most vein selvages. Isotopic evidence for syn-metamorphic fluid flow is preserved in veins and in marble layers. The chemical and isotopic data (63 analyses of individual samples from 22 vein systems) suggest that the area adjacent to the HBF was a zone of focused flow of isotopically light, chemically reactive fluids likely derived from the HBF during regional metamorphism with the greatest flow found near the fault. Post-metamorphic carbonate minerals from syn-metamorphic, foliation-parallel quartz-chlorite-carbonate veins in the biotite and garnet zones provide isotopic and textural evidence that these veins were conduits for multiple generations (prograde and retrograde) of fluid flow. Vein carbonate minerals and pervasive carbonation of a series of post-metamorphic, Carboniferous-aged porphyry dikes and adjacent metapelitic schists are isotopically consistent with hydrothermal fluid flow driven by the intrusion of the dikes.

Books / Online / Dissertations & Theses

English

July 12, 2011

Thesis (Ph.D.)--Yale University, 2004.