The Komati Formation of the Barberton Greenstone Belt is the type locality of the rock type known as Komatiites. Komatiites are ultramafic lavas that were generated and erupted mainly during the Archaean. They give insight into volcanism on the early Earth as well as the nature of the mantle and melting processes. During 2010-2011 the International Continental Drilling Programme (ICDP) Barberton Project drilled two cores (BARB 1 and BARB 2) into the Komati Formation to obtain continuous sections of the komatiite strata. These cores were drilled to gain knowledge about the structure, textures, compositions, processes and contact relationships of komatiite flows, which could not be obtained from surface outcrop because of lack of continuity and relatively poor exposure. The drill holes also intersected a volcanic tumulus unit, the first of its type recognized in komatiite lava flows, allowing insight into the processes that created the tumulus and the processes responsible for creating the differentiated komatiite flows. The core was logged in detail, revealing a variety of rock-types and styles of volcanism. The rock-types encountered range from massive and differentiated ultramafic komatiites, through komatiitic basalts to mafic basalts. Some minor later intrusions of gabbros and dolerite are also present. The komatiites and komatiitic basalts are extrusive lavas and represent continuous eruptive sequences. The gabbros are typically intrusive, but can represent late stage crystallization. Contact relationships are evident in the core, where they have not been eroded by overlying flows, and are used to distinguish 85 individual flows in BARB 1 and 65 in BARB 2. Chill margins are typically between 5 and 50 cm thick and brecciated contacts are usually 5- 15 cm thick where present. Only rare examples of original mineralogy (olivine and pyroxene) are preserved because of pervasive alteration of the rocks. Alteration minerals are serpentine, chlorite, tremolite and magnetite. Early serpentine veining was followed by later stage magnesite veining. The opaque minerals – chromite with secondary magnetite overgrowth – are mostly located at olivine grain boundaries. The tumulus unit in the BARB 1 core was created by upward doming of the upper skin of a lava tube. The unit is 90 m thick and consists of five textural sections: basal cumulates, harrisite, pyroxene spinifex, gabbro-pyroxenite and a hyaloclastite unit that caps the sequence. The cumulates contain macrocrystic olivine grains that reach 15 mm in length; they are elongated and rounded, aligned in certain horizons and are tightly packed, with a maximum of 20 % matrix. The harrisite is a form of skeletal olivine (with crystals up to 5 cm in length) that grew upwards from the underlying cumulate layer. Between the skeletal olivine crystals are small (< 2 mm) crescent-shaped pyroxenes contained within the melt residue. Pyroxene grains in the spinifex lava reach 20 cm in length and are surrounded by a fine-grained matrix. The gabbro and pyroxenite layers contained within the spinifex layer are interpreted to represent the last stage of crystallization within the structure since they are chemically related to the tumulus and no chill margins are present between the gabbro and surrounding pyroxene spinifex. Both the spinifex and gabbro contain unaltered pyroxene crystals and the gabbro also contains relatively fresh plagioclase. The hyaloclastite breccia consists of fragmented fine-grained chill margin blocks derived from the upper crust of the lava tube. The fragments are surrounded and supported by a glassy shard-like matrix. Inflation processes are evident in the tumulus and gave rise to multiple layers of large elongated olivine cumulates together with the upward and outward bulging of the upper crust to form a hyaloclastite breccia. Chemically the tumulus exhibits a Fo93 olivine control. Fractionation processes are clear in MgO vs. depth, binary diagrams and REE plots. Element concentrations are between 1 and 11 times chondrite with a very small LREE enrichment. Differentiated komatiite flows are composed of three lithologies: basal cumulates, olivine spinifex and chill margin zones. The cumulus olivines have a crystal size of 0.5-1 mm, are euhedral and enclosed by a 30 to 60 % melt component. The spinifex olivine forms random or parallel sheets on a centimetre scale and is completely altered to serpentine. Between the olivine spinifex are chemically more evolved pyroxene spinifex blades, which are smaller (millimetre to centimetre scale) and altered to a combination of serpentine-chlorite-tremolite. The fine-grained chill margins of the flows are typically 1-10 cm wide and in some cases contain contact breccias or hyaloclastites. Three packages of differentiated komatiite flows occurring at several stratigraphic intervals where sampled in detail. The lowest package BARB 1 (89-118 m) exhibits chemical trends that are interpreted to indicate a combined crystallization control by olivine and pyroxene. This is evident in the rock compositions and by petrographic studies that reveal the presence of two cumulus phases. The chemical compositions of the other two differentiated packages, BARB1 (378-420 m) and BARB 2 (252-274 m) are controlled by crystallization or accumulation of Fo93 and Fo94, respectively. These packages have olivine cumulates which are surrounded in some cases by pyroxene oikocrysts. In some samples the pyroxenes have unaltered cores. The REE plots are well constrained between 2 and 9 times chondrite values, and have slight LREE enrichment. The tumulus structure and differentiated flow packages BARB 1 (378-420 m) and BARB 2 (252-274 m) have similar mineralogies and compositions but contain different textures. This is attributed to the size of the tumulus in comparison to the differentiated flows and implies similar magma processes and origins for all three units. The BARB 1 (89-118 m) interval appears to have undergone slightly different processes, as indicated by the presence of the two cumulus phases. This package is also altered to a greater extent than the others and no unaltered pyroxene is present.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / The ca. 36 Ma Chesapeake Bay impact event on the east coast of Virginia, USA, formed an 85 km complex crater in Cretaceous to Eocene sediments and underlying crystalline basement rocks belonging to the Appalachian orogen. Appalachian rocks are well exposed along the Appalachian Mountains to the west, however, little is known of the basement along the Atlantic Coastal Plain owing to the covering sedimentary sequence. This study investigates the crystalline rocks intersected by the 2006 ICDP (International Continental Scientific Drilling Program) – USGS (United States Geological Survey) drilling of the Chesapeake Bay impact structure (CBIS) on the Eyreville Farm near Cape Charles, Virginia. The crystalline rocks of the Eyreville-B borehole core are found in the lower basement-derived section (between 1551.19 m and 1766.32 m depth), in the amphibolite megablock (between 1376.38 m and 1389.35 m depth) and in the upper granite megablock (between 1095.74 m and 1371.11 m depth). The lower basement-derived section consists of foliated metasediments, which include mica schist, amphibolite and calc-silicate rock, and coarse-grained to pegmatitic granite. The amphibolite megablock is a black to dark grey to dark green, fine- to medium-grained, locally foliated, relatively homogenous, lithic block. The upper granite megablock is divided into gneissic and massive varieties, with a minor component of biotite schist xenoliths. The crystalline rocks contain foliations and related structures, fractures and breccias, microstructures and porphyroblast microstructures; however, none of the three lithic blocks is in situ and, consequently, structural measurements cannot be fully interpreted tectonically. Mineral assemblages and microstructural evidence in the mica schists suggest the rocks in the lower basement-derived section experienced a syn-D1 amphibolite facies peak metamorphic event (M1a) followed by retrograde metamorphic conditions (M1b) limited to D1b mylonitic and D2 brittle deformation. Similar metamorphic conditions in the upper megablocks suggest that the three sections likely formed part of a single metamorphic terrane. iv Geochemistry in the lower basement-derived mica schists revealed a strong intermediate igneous provenance, whereas the upper megablock biotite schist xenoliths showed a quartzose sedimentary provenance; the precursors to both appear to have been deposited in active continental margin settings. The lower basement-derived amphibolite appears to be derived from a sedimentary source. The precursor to the upper amphibolite megablock, on the other hand, was probably a tholeittic gabbro generated in an island arc setting. The peraluminous, S-type nature of the lower basement-derived granite suggests it was most likely generated in a within-plate tectonic setting. In contrast, the massive and gneissic granites from the upper megablock are metaluminous, I-type granites that were most likely generated in a syn-collisional environment. Metamorphic conditions of the M1 event were constrained using mineral assemblages mainly from the lower basement-derived section, which limited the X(H2O) value to 0.8, P to >0.4 GPa and the T range to 600-670°C. Using the 0.4 GPa pressure constraint, Zr-in-rutile thermometry revealed a peak metamorphic temperature for the M1 event of 606 ± 18°C, which is consistent with mid-amphibolite facies metamorphism. These estimates suggest a very steep geothermal gradient approaching ~44°C/km. Rutile U/Pb geochronology revealed that the M1 event recorded in the lower basement-derived metasediments occurred at 259 ± 13 Ma, with Ar/Ar geochronology indicating the cooling path through to greenschist metamorphic conditions. Zircon U/Pb SHRIMP geochronology performed by Horton et al. (2009b) on the massive and gneissic megablock granites dated their crystallisation ages at 254 ± 3 Ma and 615 ± 7 Ma, respectively, with the former age in agreement with the rutile U/Pb peak metamorphism results from the lower basement-derived section. These ages, together with petrography, structural observations, geochemistry and geothermobarometry suggests that the amphibolite and granite megablocks form part of the same metamorphic terrane as the lower basement-derived section and that the D1 and M1 events recorded in the lower basement-derived section and upper megablocks of the Eyreville-B borehole core likely occurred during the late stages of the Alleghanian orogeny. v Based on mineralogy, geochemistry, metamorphic grade and structural evidence, comparisons with the neighbouring terranes within the Appalachian basement beneath the Atlantic Coastal Plain sediments suggest that the lower basement-derived and upper amphibolite and granite megablocks of the Eyreville-B borehole core most likely formed part of the Hatteras terrane prior to the Chesapeake Bay impact event. This terrane, together with 5 other terranes, forms part of the Carolina Zone, a peri-Gondwanan micro-continent formed by the amalgamation of magmatic arcs during the Penobscottian and Taconian orogenies, which was then accreted onto the Laurentian margin during the Salinic and Acadian orogenies.

This creative report deals with the project of photographing a remote area in· Southern Idaho, near Almo, called City of Rocks. The photographer worked in the tradition of "Straight Photography." The goal was not to document the area but to make images about what one might feel from the subjects rather than images about the subject. The hope was that the resulting photographs would have a "life sense of their own."

Graduation date: 1995

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 276-317). Also available in print.

Thesis (M.A.)? -- Zhongguo wen hua xue yuan. / Cover title. Reproduced from typescript. Includes bibliographical references (p. 93-98).

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xii, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 53-54).

published_or_final_version / Applied Geosciences / Master / Master of Science

published_or_final_version / Applied Geosciences / Master / Master of Science

The Paleoproterozoic Jiao-Liao-Ji Belt (JLJB) is a NNE-SSW trending continental belt lying in the Eastern Block of the North China Craton, with its southern segment extending across Bohai Sea into the Jiaobei massif. Little work has been done in the southern segment of the belt, and thus the timing for metamorphism and tectonic nature of the JLJB are still controversial, with models ranging from those invoking continent-arc-continent collision to those advocating rifting closure. The presence of the high-pressure pelitic and mafic rocks of the Jiaobei massif (Eastern Shandong) located in the southern segment is crucial to these controversial isues. The aim of this study is to resolve these issues through an integrated study including field study followed by geochronological and metamorphic investigations on the high-pressure pelitic and mafic rocks in the Jiaobei massif. Metamorphic zircons from two high-pressure mafic granulites and one metamorphic zircon from a garnet-sillimanite gneiss have 207Pb/206Pb ages of 1884–1956 Ma and 1939 ± 15 Ma respectively, which are in accordance with the metamorphic ages of 1.93–1.90 Ga previously obtained from the northern segment of the JLJB. Metamorphic zircons from a high-pressure pelitic granulite and two politic gneisses have weighted mean 207Pb/206Pb ages of 1821–1837 Ma, while those zircons from two associated marbles analyze similar weighted mean 207Pb/206Pb ages of 1790–1817 Ma. These metamorphic ages are consistent with the metamorphic ages of c. 1.85 Ga produced from the Ji’an Group in the northern segment of the JLJB and 1.86-1.80 Ga produced from the high-pressure pelitic granulites of the Jingshan Group in the southern segment of the belt. As this metamorphic event happened synchronously with the intrusion of the A-type granites in the Jiao-Liao-Ji Belt and adjacent regions, it is considered to have resulted from the contact metamorphism caused by the emplacement of the post-orogenic or anorogenic mafic and granitic plutons that are widespread in the belt. The high-pressure pelitic granulites recently discovered in the Jiaobei massif, and the medium-pressure pelitic granulites and high-pressure mafic granulites, were examined with an integrated study including petrology, mineral chemistry and pseudosection modeling. By applying the THERMOCALC technique, pseudosection modeling on the high-pressure and medium-pressure pelitic granulites in the NCKFMASHTO system and on the high-pressure mafic granulites in the NCFMASHTO system was constructed to confine the P-T conditions and P-T paths. The results show that the peak P-T conditions of the high-pressure pelitic granulites, high-pressure mafic granulites and medium-pressure pelitic granulites are 14.8–16.2 kbar/860–890°C, 13.1–15.1 kbar/780–890°C and 9.4–10 kbar/870–900°C, respectively, and that the metamorphic evolution of all these granulites is characterized by clockwise P-T paths involving decompression and cooling after the peak metamorphism, implying that subduction/collision-related processes must have been involved in the development of the southern segment of the Jiao-Liao-Ji Belt. By combining the geochronological and metamorphic data, the results of this study suggest that the JLJB represented a Paleoproterozoic rift-and-collision belt along which the Longgang and Nangrim blocks amalgamated to form the Eastern Block at 1.93–1.90 Ga. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy