Physical Sciences and Mathematics Commons^™

Major- And Minor-Element Analysis Of Apollo 14 Volcanic Green Glasses B, And Petrogenic Modeling Of Apollo 14 Green Glasses A And B, Vera Assis Fernandes

Geology Theses and Dissertations

The lunar picritic volcanic glasses have been identified as being quenched samples of primary magmas extruded onto the lunar surface via fire-fountains. The study of the composition of these glasses is of extreme importance for the understanding of the Moon's mantle composition and petrogenetic processes.
Based on their chemical signature (low-Ti and high Mg#) and physical characteristics, the lunar picritic glasses are believed to represent primary magmas. Experimental data suggest that these melts formed at 360-500 km depth (18-25 kbar) in the lunar mantle, and were transported onto the lunar surface through a "channel" network (McKenzie, 1985b) that isolated these …

Petrology And Major Element Geochemistry Of Basaltic Glasses From The Blanco Trough, Northeast Pacific, Glenn A. Gaetani

Geology Theses and Dissertations

The original electron microprobe analyses of suite of basaltic glasses recovered in 1968 by W.G. Melson and co-workers from the Blanco Trough have extremely unusual characteristics. Their compositions plot in a region of the normative Ol-Di-Pl-SiO2 tetrahedron which suggests that they represent liquids in equilibrium with an upper mantle assemblage of olivine + orthopyroxene at 10-15 kb. Given the present state of controversy surrounding the composition and depth of origin of primary MORB, natural examples of such liquids would be very important. The major element variations observed in the suite imply that the dominant phases are olivine and an iron-aluminum …

Petrology Of The Kula Volcanic Field, Western Turkey, Julie M. Dyer

Geology Theses and Dissertations

The Kula volcanics are a small Pleistocene to Recent volcanic field located on the north shoulder of the Gediz graben, approximately 120 km east of Izmir. The field consists of a mixture of flows, small cones and pyroclastic deposits erupted during three periods of volcanic activity beginning about one million years ago. The volcanics range in composition from basanites to trachybasalts, commonly porphyritic with abundant clinopyroxene, olivine and amphibole phenocrysts. The lavas also host a wide variety of megacrysts, crustal xenoliths and hydrous mantle-derived nodules. These volcanics unconformably overlie Neogene lacustrine sedimentary rocks and the metamorphic basement rocks of the …

The Geology Of The Oceanographer Transform Fault, Richard H. Moody Jr.

Geology Theses and Dissertations

A detailed survey of the Oceanographer transform fault and environs at 35º N, 35ºW has yielded detailed information with respect to the generation and evolution of seafloor at a slowly accreting plate margin. From this data detailed bathymetric maps and maps of depth to basement have been constructed for a swath of seafloor 1800 km long and 100-200 km wide centered about the offset region. This data was used to subdivide major phases of seafloor spreading during the Tertiary. The ridge crest and all major topographic features near the transform appear to be affected by their proximity to the transform. …

Geology Of The Mafic/Ultramafic Transition, Table Mountain, Western Newfoundland, Suzanne O'Connell

Geology Theses and Dissertations

A thin (<200 m.) mafic suite and well developed mafic/ultramafic transition zone are exposed above a flat lying peridotite contact on northwestern Table Mountain. The igneous layering and sedimentary features indicate mineral deposition under conditions which promoted adcumulate growth, were capable of minor transport, and were subjected to at least minor tectonic activity during consolidation. Feldspathic,. mafic, and ultramafic dikes and veins cross-cut the layering. Microscopic futures indicate deformation at elevated temperature and/or low strain rates. Deformation is best developed within the transition zone, but cataclastic zones are most common in the hornblende gabbros. Orientations of layering, foliation, and lineation indicate a variable mafic/ultramafic transition and macroscopic folding. Geometric analysis indicates three distinct fold axis orientations: an east-west horizontal fold axis, a northeast trending modestly plunging axis, and a vertical though poorly defined axis. Such features demonstrate that an apparently simple contact relationship may be extremely complex. This has important implications for ocean floor accretion. The relatively simple ocean floor seismic stratigraphy masks very complex petrological and structural processes. Such processes may involve deposition in an actively convecting magma chamber with a differentially subsiding wedge (Dewey and Kidd, 1977), in which folding occurs in response to the steepening angle between the cumulate banding and the base of the magma chamber. The instability is enhanced by the different accumulation rates and densities of the minerals involved. The lineation may originally be a sedimentary feature indicative of transport direction from the convection cell, and perpendicular to the compressive stress which produced. the folding. The different orientations of lineations and fold axes could be produced by rotation of the ocean crustal blocks during lateral transport along the ocean floor and/or obduction. Further detailed study of ophiolite complexes will continue to shed light upon the nature and development of oceanic crust.

Petrology And Mineral Chemistry Of Some Jan Mayen Volcanics, Carla A. White

Geology Theses and Dissertations

The island of Jan Mayen is the northernmost active volcano on the Mid-Atlantic Ridge. The rocks of Jan Mayen belong to the potassic series of the alkaline rocks and appear to belong to the straddle type association. The ankaramites and alkali olivine basalts are characterized by the presence of large xenocrysts of rimmed chromium diopside, titaniferous salite, olivine (Fo83 to Fo88), magnetite and sometimes plagioclase (bytownite rimmed by labradorite). Phenocrysts of olivine (Fo74) and plagioclase (andesine) are present in several rocks. These and phenocrysts lie in a matrix composed of` titaniferous salite, olivine (Fo58), plagioclase (andesine), magnetite, biotite and sometimes …

Geology Of The Lucea Inlier, Western Jamaica, Jack Grippi

Geology Theses and Dissertations

The Lucea Inlier exposes a Santonian to Campanian 4 km + thick sequence of shale-siltstone, resedimented volcaniclastics, lenses of shallow-water limestone, micritic limestone, pebbly mudstone and sandy pebble to boulder conglomerate. Clastics were deposited by a variety of gravity flow mechanisms. Petrographically sandstones are lithic or feldspathic arenites and contain only very small amounts of detrital quartz. Structurally the inlier is characterized by simple, open, east-west trending folds. A spaced, vertical axial-planar cleavage is developed in shales and fine siltstones. Two major east-west trending left-lateral fault zones, the Fat Hog Quarter and Maryland faults, cut the inlier into three blocks, …

Petrology Of The Oceanographer Fracture Zone (35ºn35ºw), Tsugio Shibata

Geology Theses and Dissertations

During a geological and geophysical survey of the Oceanographer Fracture Zone (35°N, 35°W), seventeen dredge hauls containing a variety of rocks were obtained. Petrographic study shows that these rock samples can be classified into six main rock types: fresh basalt, weathered basalt, metabasalt, gabbro, metagabbro, and serpentinite. Most of the dredge hauls were positioned on the steep, southern wall of the fracture zone, and an inference from the dredging results suggests that basalt is the most abundant rock type which outcrops at the junction between the rift valley and the fracture zone; however, as we move away from the junction, …

Structural Studies In The Mafic And Ultramafic Rocks Of The Lewis Hills, Western Newfoundland, Jeffrey A. Karson

Geology Theses and Dissertations

Table of contents:
CHAPTER I. INTRODUCTION
CHAPTER II. REGIONAL GEOLOGY
CHAPTER III. THE LEWIS HILLS COMPARED TO THE NORTHERN AREAS OF THE BAY OF ISLAND COMPLEX
CHAPTER IV. PETROGRAPHY
CHAPTER V. STRUCTURAL GEOLOGY
CHAPTER VI. SUMMARY, CONCLUSIONS, AND SPECULATIONS
BIBLIOGRAPHY
APPENDIX I. CONTOURED STEREOGRAPHIC PROJECTIONS OF FOLIATIONS AND LINEATIONS IN THE HINES POND AREA

A Study Of Some Petrologic And Structural Aspects Of The East Dover Ultramafic Bodies, South Central Vermont, Mark Allen Hoffman

Geology Theses and Dissertations

INTRODUCTION (pp.1-4)

Mineralogical, textural and chemical changes of ultramafic rocks in response to regional deformation and metamorphism are, at best, imperfectly known (Miyashiro, 1973, p. 30). In Vermont, which has an extremely prominent and well-exposed belt of ultramafics (fig. 1), investigation of these rocks has largely been directed toward such processes as serpentinization, steatitization, and the formation of metasomatic zones at the contacts with country rocks. With few exceptions, there is a lack of detailed descriptions of regional metamorphic textures, mineralogy, and structures developed in the Vermont ultramafic rocks. It is the main purpose of this thesis to describe the …

Petrography, Metamorphism, And Geochemistry Of The Bermeja Complex And Related Rocks In Southwestern Puerto Rico And Their Significance In The Evolution Of The Eastern Greater Antillian Island Arc, Victor J.B. Lee

Geology Theses and Dissertations

Chapter I. Introduction and previous work 1
Chapter II. Geological setting and the petrography of the igneous and metamorphic rocks from southwestern Puerto Rico 6
Chapter III. Metamorphism in southwestern Puerto Rico and relations to the Eastern Greater Antilles 46
Chapter IV. Geochemistry of the Bermeja complex 84
Chapter V. Secular compositional changes of the volcanic rocks in Puerto Rico and other islands in eastern West Indies and the significances of the Bermeja complex 179
Appendix A-E: Petrographic data of the analyzed samples of the Bermeja complex 222
References cited 231

Petrology Of The Nemeiben Lake Ultramafic And Associated Nickel-Sulphide Deposits, Anantaramam Peddada

Geology Theses and Dissertations

The Nemeiben Lake ultramafic body is located in the center of Saskatchewan, Canada, within the Churchill Province of the Canadian Shield. The ultramafic rocks consist of serpentinites, partly serpentinized and uralitized pyroxenite, and unaltered pyroxenite. Associated sulphide mineralization is of disseminated, net texture, and fracture filling types. The ore minerals present are pyrrhotite, pentlandite, chalcopyrite, pyrite, marcasite, violarite, bravoite and native copper. The sulphides are considered to be initially of magmatic origin formed from a sulphide melt separated at a late stage during crystallization of the ultramafic rocks. Subsequent serpentinization has locally redistributed the ores.
Serpentinization in the Nemeiben Lake …

Origin Of The Mount Merino Chert And Shale, Middle Ordovician, Eastern New York State, Dorothy M. Lang

Geology Theses and Dissertations

Mount Merino Chert and Shale, Middle Ordovician, is one of the most siliceous units of the Taconic sequence (eastern New York and western Vermont); it is composed of interbedded shale, siliceous hale, argillite and chert. Non-clastic quartz — aggregates of quartz having a.mosaic or felted texture — predominates in all beds, except `shale. All siliceous beds are finely laminated; most laminae are distinguished from adjacent laminae by the texture of the quartz groundmass, and the amount of clastics, carbonates, chlorite and sulphides. Statistical comparison of the textures of the quartz aggregates which occur with the other mineral components suggests that …