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Showing 1 to 20 of 115 for “"petrogenesis"”.
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Petrogenesis of the Eshowe melilitites
The Eshowe melilitites intruded marginal cratonic crust at approximately 80my. Their intrusion followed after a long period of extensive rift tectonism associated with the breakup of Gondwanaland. The intrusives represent the final phase of alkaline and basaltic magmatism that commenced at about …
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Silicate Melt Inclusions in Igneous Petrogenesis
Silicate melt inclusions are ubiquitous in quartz phenocrysts, yet there are few studies of such inclusions from porphyry copper systems. A melt inclusion forms when magma is trapped in a growing phenocryst. If a phenocryst is able to preserve the original parent magma, then accurate information …
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Petrogenesis of the Moosehorn igneous complex, Maine
New radiometric ages and field relations within the Coastal Maine Magmatic Province suggest a bimodal distribution of igneous rocks in both space and time. The earlier magmatic event is represented by the development of large igneous complexes which occur along a magmatic axis extending from Calais …
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Petrogenesis of the Springfield Granodiorite, southeast Pennsylvania Piedmont
The Springfield pluton intrudes the Wissahickon schist in the southeast Pennsylvania Piedmont. The mineralogy of the pluton. in order of decreasing abundance is plagioclase, quartz, microcline, biotite, epidote (often with allanite cores) and trace amounts of hornblende. Accessory minerals include …
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Petrogenesis of the Spruce Pine pegmatites, North Carolina
Pegmatites in the Spruce Pine district, North Carolina, are an example of muscovite class pegmatites that were derived from differentiation of a magma. There are eight granodiorite plutons in the Spruce Pine area ranging in size from 1 to 20 square kilometers that contain and are surrounded by …
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Element fractionation in the petrogenesis of ocean island basalts
Analytical techniques have been developed to measure the very small [230ThP32Th] atomic ratios (3-8x10-6) typical of basaltic lavas using a single focussing mass spectrometer. Compared to conventional alpha-counting methods, the technique presented typically gives a 2-5 fold improvement in …
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The Origin and Petrogenesis of the Ethiopian Flood Basalts
The volcanic rocks of the Afro-Arabian volcanic province chart the nature and evolution of the mantle plume source responsible for a major continental flood basalt event and the manner in which it interacted with the lithosphere over the course of continental separation. The flood basalts of the …
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Trace element zoning in garnets--implications for metamorphic petrogenesis
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1988.
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Petrogenesis of the reversely zoned Turtle pluton, Southeastern California
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 …
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Applications of Melt Inclusions to Problems in Igneous Petrogenesis
… and field studies to better understand igneous petrogenesis. One potential problem associated with melt inclusions is water-loss during laboratory heating. A Raman spectroscopic technique was developed to determine water contents of silicate glasses, and this technique was applied to monitor …
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Petrogenesis and thermal history of the Kunlun Batholith, Northern Tibet
The Kunlun Terrane is the most northerly of the several microplates that comprise the Tibetan Plateau. Geochronological data from the Kunlun batholith defines three distinct periods of intrusion at 390 Ma, 250 Ma and 190 Ma. A model is presented whereby the Devonian intrusions are considered to be …
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Petrogenesis of crustal xenoliths from San Carlos Indian Reservation, Arizona
Includes bibliographical references (pages 165-173).
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The petrogenesis of Liberian diamondiferous rocks, Man Craton, West Africa
Kimberlites and lamproites are ultramafic igneous rocks believed to originate from the convective asthenosphere and sub-continental lithospheric mantle, respectively, however, the genetic link between these rock types is still a debate among researchers. Recently, it has been shown (e.g., in the …
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Petrogenesis of a migmatite, Penobscot County, Maine: ultrametamorphism or intrusion?
The Clifton Migmatite crops out between the biotite grade Bucksport Formation (predominantly calcareous pelitic quartzite) on the west, the Lucerne Pluton (biotite granite) on the southeast, and the Parks Pond Pluton (mafic granite to quartz syenite) on the northeast. The Parks Pond crystallized at …
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Geochemistry and petrogenesis of the Catoctin Volcanic Province, central Appalachians
The Catoctin Volcanic Province represents a sequence of rift related tholeiitic magmas erupted during late Precambrian opening of the Iapetus ocean basin. Three transects have been mapped across the province in northern Virginia in order to demonstrate that there is a mappable stratigraphy and to …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
To explore the ability of melting mafic lithologies to produce alkaline ocean-island basalts (OIB), an experimental study was carried out measuring clinopyroxene (Cpx)- melt and garnet (Gt)-melt partition coefficients during silica-poor garnet pyroxenite melting for a suite of trace elements, …
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Stratigraphy and petrogenesis of the Parana continental flood basalts, southern Brazil
The Early Cretaceous (~130 Ma) Paraná lavas of South America represent the largest preserved example of a continental flood basalt (CFB) province, with a present area in excess of 1.2 x 10<sup>6</sup> km<sup>2</sup>. Magmatism is dominated by tholeiitic basalts (> 90 %), with minor rhyolites as a …
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Geochemistry and petrogenesis of the Proterozoic Pater metavolcanic suite, Spragge, Ontario /
The Pater metavolcanic suite (PVS) was extruded as part O'f the basal Pater Formation of the Huronian Supergroup ca. 2.4 Ga. They Ars classified as wi thin-plate tholeiites associated with an immature ri-fting episode, and are inter layered with associated vol cani clastic and metasedimentary …
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Petrogenesis of the False Bay dyke swarm, Cape Peninsula, South Africa
The False Bay dyke swarm is the southern-most set of Early Cretaceous dolerite dyke intrusions along the western margin of southern Africa associated with rifting of Gondwana and opening of the South Atlantic Ocean. Previous work highlighted the evolution of a single magma type from …
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Petrogenesis of the Northwest corner intrusive phases, Dutoitspan kimberlite, South Africa
The Outoitspan Group 1 kimberlite pipe forms part of the well-known cluster of pipes located in and around the city of Kimberley, South Africa. Eight macroscopically distinct intrusive phases, i.e. D2 Type 2, D2 Type 3, D2/D5, D5, D18, Type 5, D16 and the D16 dyke are present in the Northwest …
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