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- 주제어 : PETROLOGY (검색결과 84 건)
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조석주 The University of Texas at Austin 2004 해외박사
Pennsylvanian calcareous algal bioherms dominated by Donezella, Beresellid, and Cuneiphycus could potentially form prolific hydrocarbon reservoirs. Understanding the biological makeup and depositional settings of these carbonate buildups is imperative. To provide an understanding of the geological and biological processes controlling the formation of these buildups, three localities in the southern United States were studied by integrating field sampling, microfacies analysis, and microstratigraphic analysis. A Lower Pennsylvanian Donezella- and siliceous sponge-dominated carbonate buildup from the Wapanucka Formation, Oklahoma is composed of irregular pockets of boundstone dominated by Donezella, worm tubes, microbial peloids and micrite, siliceous sponge spicule, and peloidal wackestone with other bioclasts. The most significant finding of this study is the recognition of delicate a Donezella framework or colony of thalli enclosing and forming constructional pores. Upper Pennsylvanian Beresellid algal colonies from the Holder Formation, New Mexico, are the product of an in situ growth fabric and constituents of Beresellid algal colonies. The Beresellid boundstone fabric was created by bundles of tangled algal thalli growing at an angle or parallel with the bedding surface, in association with phylloid algae, foraminifera, Tubiphytes, and rare brachiopods and crinoid fragments. The Lower Pennsylvanian Cuneiphycus-dominated buildups from the Marble Falls Formation, Texas are composed of irregular pockets of boundstone dominated by Cuneiphycus, Donezella boundstone, and peloidal wackestone with other bioclasts. The first account of the red alga Cuneiphycus building a delicate framework of thalli and building a small-scale framework is documented. In order to effectively handle large numbers of digital images of thin sections used in this study, a new method for creating and authoring virtual carbonate thin sections in PDF format was devised that it is a highly flexible, and platform independent image digitization and content creation method. The significance of this approach is that an image of the thin section is preserved/created and as well as preserves a variety of valuable information about a specimen that can be directly linked to the image of the specimen itself. Another method of building a digital petrography image archive was devised to supplement the labor-intensive nature of teaching optical petrography. The architecture, process, and lessons learned from developing an interactive multimedia CD-ROM tutorial in sandstone petrology for undergraduates is documented. This approach provides possible models for similar development in other fields of petrography or in any other field that utilizes large quantities of visual material, such as seismic or remote-sensing image interpretation.
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조석주 Graduate School of The University of Texas 2004 해외박사
Pennsylvanian calcareous algal bioherms dominated by Donezella, Beresellid, and Cuneiphycus could potentially form prolific hydrocarbon reservoirs. Understanding the biological makeup and depositional settings of these carbonate buildups is imperative. To provide an understanding of the geological and biological processes controlling the formation of these buildups, three localities in the southern United States were studied by integrating field sampling, microfacies analysis, and microstratigraphic analysis. A Lower Pennsylvanian Donezella- and siliceous sponge-dominated carbonate buildup from the Wapanucka Formation, Oklahoma is composed of irregular pockets of boundstone dominated by Donezella, worm tubes, microbial peloids and micrite, siliceous sponge spicule, and peloidal wackestone with other bioclasts. The most significant finding of this study is the recognition of delicate a Donezella framework or colony of thalli enclosing and forming constructional pores. Upper Pennsylvanian Beresellid algal colonies from the Holder Formation, New Mexico, are the product of an in situ growth fabric and constituents of Beresellid algal colonies. The Beresellid boundstone fabric was created by bundles of tangled algal thalli growing at an angle or parallel with the bedding surface, in association with phylloid algae, foraminifera, Tubiphytes, and rare brachiopods and crinoid fragments. The Lower Pennsylvanian Cuneiphycus-dominated buildups from the Marble Falls Formation, Texas are composed of irregular pockets of boundstone dominated by Cuneiphycus, Donezella boundstone, and peloidal wackestone with other bioclasts. The first account of the red alga Cuneiphycus building a delicate framework of thalli and building a small-scale framework is documented. In order to effectively handle large numbers of digital images of thin sections used in this study, a new method for creating and authoring virtual carbonate thin sections in PDF format was devised that it is a highly flexible, and platform independent image digitization and content creation method. The significance of this approach is that an image of the thin section is preserved/created and as well as preserves a variety of valuable information about a specimen that can be directly linked to the image of the specimen itself. Another method of building a digital petrography image archive was devised to supplement the labor-intensive nature of teaching optical petrography. The architecture, process, and lessons learned from developing an interactive multimedia CD-ROM tutorial in sandstone petrology for undergraduates is documented. This approach provides possible models for similar development in other fields of petrography or in any other field that utilizes large quantities of visual material, such as seismic or remote-sensing image interpretation.
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Stiegler, Melanie Thompson Stanford University 2009 해외박사(DDOD)
소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.
This dissertation contributes to the on-going effort to develop a synthetic view of the evolution of the Earth's mantle and its surface systems through analysis of komatiitic volcaniclastic deposits in the 3.5-3.2 Ga Barberton greenstone belt, South Africa. Komatiites are rare ultramafic volcanic rocks that were almost exclusively erupted during the first 2 Ga of Earth's history. They have served a prominent role in interpreting Archean mantle composition and physical conditions but the pervasive alteration affecting all Archean rocks has led to multiple models of their melting conditions and tectonic settings. There have been few reports of komatiitic pyroclastic debris and limited modern volcanological data has been collected on these deposits. Consequently, little is known about the origins of these pyroclastic rocks and their potential contributions towards a more comprehensive understanding of komatiite petrology. Chapter 1 describes the physical and geochemical characteristics and distribution of numerous current-worked and graded ashfall deposits in the Barberton greenstone belt that have either high refractory element contents or ratios of immobile elements consistent with those of komatiitic flow rocks. Results of this study show that komatiitic volcanism, which is usually described as almost exclusively effusive, could also be highly explosive. The abundance of these tuffs throughout the stratigraphic record reveals that large-scale komatiitic eruptions played a significant role in greenstone belt development for over 200 million years. Chapter 2 uses the chemical compositions and textures of these explosively fragmented komatiitic tuffs to decipher multiple episodes of post-depositional alteration, which have dramatically affected original element abundances and disguised primary magmatic signatures in many of the samples. Despite this significant metasomatic overprint, primary ratios of Al, Ti, and the high field strength elements are demonstrably retained, allowing for petrogenetic comparisons with the associated komatiitic flow rocks. Most of the tuffs are aphyric, which suggests that these komatiites were erupted as superheated or near-liquidus anhydrous melts and supports their derivation in mantle plumes. Geochemical, stratigraphic, and geochronologic data demonstrate that intervals of komatiitic volcanism in Barberton are highly diverse in terms of eruptive rates, volumes, and magma compositions, suggesting a variety of plume-plate interactions and/or variation in proximity to eruptive centers. Chapter 3 investigates the physical mechanisms and environmental conditions that enabled multiple episodes of explosive komatiitic volcanism recorded in the Barberton belt. Documentation of bed and clast textures and stratigraphic relationships reveals that explosive komatiitic eruptions and the widespread distribution of ash occurred due to a combination of factors that include phreatomagmatic fragmentation at high magma-water ratios, volatile exsolution, and high discharge rates. Pyroclastic eruptions likely took place during vent shoaling of submarine volcanoes into shallow-water and/or subaerial settings. Prior to shallow-water buildup, komatiitic volcanism was either effusive, forming extensive lava plains, or resulted in moderate to low energy fragmentation, producing thick hyaloclastite lapilli tuffs and lapillistones.
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이종익 University of Tokyo 1991 해외박사
한국 경상분지 남부에 분포하는 천소관입 화강암류들은 단일암체내에 대소규모의 미문상 화강암류를 동반하고 있다. 이들 미문상화강암류들은 종래의 관입 또는 결정분 화의 산물이라기 보다는 'undercooling'이라는 개념에 기초한 마그마의 물리. 화학적 인 변화로서 설명되어 지기 때문에 화강암질 마그마의 성인을 논함에 있어 온도. 압력 조건의 변화에 따른 마그마의 진화과정을 보다 명확하게 규명할 수 있었다. 암체들에 있어서의 전암화학조성, 관입시기, 동위체 비의 특성들은 시간적, 공간적으로 system atic한 변화를 보여주고 있어 화강암질 마그마의 진화과정을 경상분지의 진화와 관련 된 tectonic한 입장에서 논할 수 있었다.
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아이슬란드 헤클라 화산에 대한 규장질 암석의 암석학 및 지구화학에 대한 연구를 수행하였다. 아이슬란드의 남동쪽 Eastern Rift Zone(ERZ) 인근에 위치한 헤클라 화산은 최근 수 십년 동안 10년 주기의 매우 규칙적인 분출활동으로 주목 받고 있다. 이러한 규칙적인 분출활동으로 형성된 분출암들을 체계적으로 획득하여 마그마활동의 변화를 고찰하는 것이본 연구의 목적이다. 현미경하에서 반정광물은 사장석, 감람석, 단사휘석 및 불투명광물로 관찰되며, 기질은 대부분 유리질로 구성된다. 본 시료는 SiO2를 기준으로 한 TAS 다이어그램 상에서 현무암, 현무암질 안산암, 안산암까지 구분되는 영역에 도시되며 문헌에 기록된 유문암성분은 본 시료에 포함되지 않았다. SiO2함량을 기준으로 한 하커 다이어그램에서는 약 45wt%에서 62wt%까지의 함량변화를 보이고 MgO 함량은 5.5wt%부근에서 감소경향에서 증가경향을 나타내는데 이것은 이 부근에서 불투명광물(haematite, ilmenite 등)의 정출로 인한 변화경향으로 해석된다. 일부 산발적인 Ni의 분포는 감람석 반정을 많이 포함한 시료들로 인한 결과라고 사료된다. 비슷한 변화추이를 나타내는 것으로는 Fe2O3와 TiO2의 변화경향에서 찾아볼 수 있는데 모두 SiO2 53-55wt% 부근에서 함량이 급격하게 감소하는 경향성을 보인다. 이것은 MgO의 경향에서도 관찰되었듯이 불투명광물들(특히, ilmenite와 titaniferous magnetite)의 정출로 인하여 Ti의 변화곡선이 급격하게 감소하는 것을 관찰할 수 있으며 Fe를 포함하는 다른 불투명광물들(magnetite, ilmenite 등)의 정출과 감람석과 휘석의 정출에 Fe이 계속 빠져나가면서 함량이 감소한 것으로 해석된다. 이들 암석의 광물지질온도계를 이용해서 계산해본 결과 현무암의 경우는 1150℃, 안산암에서는 830℃ 정도로서, 일반적인 암석의 지질온도분포와 거의 유사하다. 결과적으로 주원소와 미량원소에서 보여준 선적인 변화경향은 마그마 혼합 과정의 산물이기보다는 현무암질 모마그마의 진화산물로 보는 것이 타당하다고 여겨진다. 그러므로 위 논문에서 제시된 결과는 지하 깊은 곳에 위치한 마그마챔버로부터 분별결정화되어진 현무암에 의해 형성된 현무암질 안산암 마그마챔버들이 주기적으로 각각 마그마 포켓을 형성하는 천부지각으로 주입되었고, 차후에 일부 동화와 분별결정화를 통해 현무암질 마그마 조성의 변화가 있었음을 지시한다.
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