The volcanic and sedimentary Nsuze Group constitutes the lower part of the / Thesis (M.Sc.-Geology)-University of KwaZulu-Natal, Pietermaritzburg, 1984.

Terrane discrimination in polycyclic continental basement rocks is challenging due to high-grade metamorphism and intense deformation. Based on early USGS mapping the Blue Ridge basement in the Dellwood quadrangle of the eastern Great Smoky Mountains was proposed to consist of augen orthogneisses of Laurentian (Grenvillian) affinity interfolded with migmatitic hornblende and biotite paragneisses (“Carolina Gneiss”) and amphibolites of uncertain affinity. However, detailed study reveals that the hornblende gneiss of Hadley and Goldsmith (1963) is a heterogeneous map unit consisting of (1)metaplutonic rocks; (2) variably foliated and folded felsic orthogneisses; (3) strongly migmatitic, folded Hbl+Bt-bearing gneisses; (4) foliated and lineated garnet amphibolites Field relations, petrology, and geochemistry demonstrate that felsic orthogneisses are related to metaplutonic rocks via (post-Taconian) progressive deformation and reconstitution. Whole rock XRF geochemistry reveals likely protoliths of Hbl gneiss and Bt gneiss are geochemically similar and have common sources. U-Pb zircon geochronology and field relationships suggest felsic orthogneisses (1050 Ma,1150-1190 Ma, 1250-1300 Ma) are components of the Mesoproterozoic Grenville basement, and not part of a metamorphosed Neoproterozoic syn-rift Laurentian margin cover sequence. A previously unknown age mode for Mesoproterozoic plutonism in the southern Appalachians was discovered (~1250-1300 Ma) suggesting the presence of a component exotic to pre-Grenvillian Laurentia (Amazonia?).

The Tertiary lavas of Northern Skye, N.W. Scotland comprise a pile of flat-lying, predominantly basaltic, volcanic flows. The lavas are the earliest products of the igneous activity on Skye, later manifestations including the gabbroic Cuillin complex and the Red Hills granites. The activity occurred from approximately 65 Ma to 50 Ma (Palaeocene to Eocene) within a continental environment. The lava pile can be divided compositionally into three magma-types, the Skye Main Lava Series (SMLS), lavas of which constitute the majority of the pile, and the less abundant Preshal Mhor (PM) and Fairy Bridge (FB). This study concerns the petrogenesis of the three magma-types. The three magma-types have a normal basaltic mineralogy; phenocrysts include olivine, plagioclase and sparse clinopyroxene; groundmasses comprise varying proportions of olivine, plagioclase, clinopyroxene, and titanomagnetite. A typical flow comprises four zones: a basal amygdaloidal layer, a massive central portion possibly showing columnar jointing, a purple rotted amygdaloidal layer, and a capping red or brown bole. The fractional crystallisation of the SMLS w#s a two-stage process initially involving the precipitation of olivine (± minor Cr-spinel), and later fractionation of olivine and plagioclase ± clinopyroxene. The majority of the lavas assimilated some lower crustal Lewisian granulite en route to the surface. The most basic lavas are the most contaminated. Major and trace element modelling suggests that the SMLS magmas were generated by 15 % melting, at an above-average mantle potential temperature, within the spinel-garnet transition zone at a depth of - 100 km. The magmas subsequently last equilibrated with mantle host rocks at 15 kb (- 45 km).

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [137]-147).

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 106-127). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 106-127). Also available on the Internet.

No description available.

No description available.

The kyanite quartzites of the Willis Mountain and East Ridge deposits in Buckingham County, Virginia hosts the world's largest kyanite mine and constitute the largest known reserves of kyanite. The stratiform kyanite quartzite is overlain and underlain by quartz-muscovite schists which are in turn enveloped by biotite-amphibole gneiss of the Cambrian Chopawamsic formation, metamorphosed volcanic and volcaniclastic rocks. The entire package of rocks has been metamorphosed to amphibolite grade peak conditions of 6.5 kb and 600°C. The kyanite quartzite is very similar in bulk composition and accessory mineralogy to high-alumina rocks of probable hydrothermal origin in North Carolina, South Carolina, and Georgia, and to active stratiform hydrothermal alteration zones in Tatun, Taiwan and Otake, Japan. The major difference among these deposits is the type of aluminosilicate phase present, a reflection of the grade of metamorphism, with kaolinite and pyrophyllite appearing in unmetamorphosed deposits, pyrophyllite and andalusite appearing in zones of greenschist grade, and kyanite appearing in zones of amphibolite grade. Data from active alteration zones and mineral equilibria suggest that the kyanite quartzite was formed from intermediate volcanic rocks by hydrothermal action of acidic fluids (pH 2 to 4) at a temperature between 100 and 200°C under mildly oxidizing conditions. Alumina and silica were residually enriched as alkali and alkaline earth cations were extracted from the rock by hydrolysis. The surrounding quartz-muscovite schist was formed in the same manner by less acidic, cooler fluids. The adjacent biotite-amphibole gneiss also shows signs of partial hydrothermal alteration, such as residual enrichment of alumina represented by a kyanite and/or sillimanite-staurolite-gedrite assemblage. / M.S.

Few plutons with a reversed geometry of a felsic rim and mafic core have been described in the geologic literature. The Turtle pluton of S.E. California is an intrusion composed of a granitic rim and granodioritic core and common microgranitoid enclaves. Field observations, mineral textures, and chemistries, major and trace element geochemistry, and isotopic variability support a petrogenetic model of in situ, concomitant, magma mixing, and fractional crystallization of rhyolitic magma progressively mixed with an increasing volume of andesitic magma, all without chemical contribution from entrained basaltic enclaves. Hornblende geobarometry indicates the Turtle pluton crystallized at about 3.5 kb. A crystallization sequence of biotite before hornblende (and lack of pyroxenes) suggests the initial granitic magma contained less than 4 wt% H₂0 at temperatures less than 780°C. U-Pb, Pb-Pb, Rb-Sr and oxygen isotope studies indicate the terrane intruded by the Turtle pluton is 1.8 Ga, that the Turtle pluton crystallized at 130 Ma, that the Target Granite and garnet aplites are about 100 Ma, and that these intrusions were derived from different sources. Models based on isotopic data suggest the rhyolitic end member magma of the Turtle pluton was derived from mafic igneous rocks, and was not derived from sampled Proterozoic country rocks. Similarity of common Sr and Pb isotopic ratios of these rocks to other Mesozoic intrusions in the Colorado River Region suggest the Turtle pluton and Target Granite have affinities like rocks to the east, including the Whipple Mountains and plutons of western Arizona. P-T-t history of the southern Turtle Mountains implies uplift well into the upper crust by Late Cretaceous time so that the heating and deformation events of the Late Cretaceous and Tertiary observed in flanking ranges did not affect the study area. / Ph. D.