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Showing 1 to 20 of 69 for “"Rhyolite"”.
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Volatiles in Icelandic subglacial rhyolite
… unclear. The eruptive mechanisms of subglacial rhyolite are particularly poorly understood as such an eruption has not occurred during recent history and therefore has never been observed. Furthermore, the pre-eruptive volatile content of Icelandic rhyolite is poorly constrained. I have measured …
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Subglacial rhyolite volcanism at Torfajökull, Iceland
Subglacial rhyolite eruptions at Torfajökull, Iceland have produced a variety of volcanic edifices during the last glacial period (115-11 ka). These range from small-volume (<0.1 km<sup>3</sup>) volcanoes, such as Bláhnúkur and Dalakvíslfell, to larger volume (~1 km<sup>3</sup>) flat-topped tuyas …
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Geology, petrology and geochemistry of Traveler Rhyolite and Katahdin Pluton (northcentral Maine)
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1976.
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Geochemical and volcanological aspects of rhyolite eruptions from Taupo Volcanic Zone, New Zealand
… Rotorua eruption a stagnated cool, crystal-rich rhyolite magma was reactivated by the intrusion of hotter, aphanitic rhyolite. Such processes are rarely reported in the literature. Both OVC and TVC experienced contemporaneous changes in eruption style, mineralogy, and geochemistry following …
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Geology, Petrology, and Tectonic Setting of the Mafic Rocks of the 1480 MA Old Granite-Rhyolite Terrane of Missouri, USA
… subordinate component of the 1480 Ma old granite-rhyolite terrane of Missouri. The igneous rocks are present in the St. Francois Mountains and a drillcore from Shannon county and can be subdivided into two groups. The Silver Mines Mafic Group exhibits some "calc-alkaline" chemical affinities that …
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Petrologic, geochemical and isotopic evolution of rhyolite lavas from the Okataina, Rotorua and Kapenga Volcanic Centres, Taupo Volcanic Zone, New Zealand
… and isotopic data that focuses on the rhyolite lavas erupted from the OVC. These data have been combined with existing geochronological data and knowledge of vent positions to identify magma types, and hence provide a model for the spatial and temporal evolution of the silicic magmatic …
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The discovery of baddeleyite (ZrO2) and chrome spinel in the basal Rooiberg Group of the 2.057 Ga Bushveld Complex, South Africa: Implications for the impact and igneous scenarios for the petrogenesis of the Rooiberg Group.
The ~75 wt % SiO2 Basal Rhyolite is one of seven chemically distinct units of the Dullstroom Formation, the oldest of four formations that comprise the 4-6 km thick siliceous Rooiberg Group of the 2.057 Ga Bushveld Complex, South Africa. The discovery of composite zircon-baddeleyite grains and …
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Crystallisation history of rhyolite magmas at Tarawera volcano, New Zealand, from in-situ 238U-230Th disequilibrium dating and trace element geochemistry of zircon
Tarawera volcano formed during four intra-caldera rhyolite eruptive episodes in the Okataina Volcanic Centre (OVC), New Zealand, at 21.9, 17.7, 13.7, and 0.7 ka that were all triggered by basalt intrusion. Most of the episodes involved at least two distinct magma types that were erupted from the …
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Significance of magma mingling and mixing during the formation of the host-rock successions of Archean massive sulfide deposits in the Noranda camp, Abitibi subprovince, Quebec, The
… West area. In this area, a large flow-banded rhyolite cryptodome containing abundant mafic xenoliths is exposed. To characterize the occurrence of the mafic xenoliths, the shape, trend, size, and contact relationships were recorded for each xenolith. Volcanic facies analysis showed that …
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Volcanic stratigraphy and lithochemistry of the lower Jurassic Hazelton group, host to the Eskay Creek precious and base metal volcanogenic deposit
… mineralization. 21 Zone deposit foot wall rhyolite is part of a linear felsic flow dome complex several kilometers long on the western limb of the Eskay Creek antic line. Dikes feed the rhyolite domes. Four distinct rhyolite flow dome facies have been defined including peripheral facies of …
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Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction
… isotope composition of the southern Etendeka rhyolite (δ¹⁸O = + 11.5‰). It is suggested that the assimilant may have been derived from the same source as the southern Etendeka rhyolite, as opposed to the rhyolite itself, which would be expected to occur at a high crustal level. Simple oxygen …
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Geochemistry of Tl and selected elements in four Carlin-Type Gold deposits
… sediment hosted precious metals deposits and a rhyolite hosted precious metals deposit from the western United States have been analyzed for Ag, Au, Ba, Cu, I, K, Li, Mn, Pb, Rb, Sr, Tl, and Zn, and the relationship between Tl, Rb, and Kin mineralized and unmineralized rocks has been studied. …
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Prelude to the Tshirege caldera-forming eruption of the Bandelier magmatic system, New Mexico, USA
… cargo of the inter-caldera Valle Toledo Member rhyolites. Following the Otowi caldera-forming eruption of fayalite-bearing rhyolite at 1605.4 ± 2.3 ka, post-caldera rhyolites are mostly either biotite-bearing lava or pyroxene and/or hornblende-bearing tephra. During the first 8.1 ± 6.8 kyr …
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Fluid/rock Interaction History of a Faulted Rhyolite-Granite Contact, Eastern Rhine Graben Shoulder, SW-Germany : Alteration Processes Determined by Sr- Pb-Isotopes, Th/U-Disequilibria and Elemental Distributions
… element distributions across the faulted granite-rhyolite contact. The Schauenburg fault zone is situated along the eastern Rhine Graben shoulder, close to Heidelberg (SW-Germany). Major and trace element analyses allow to obtain information concerning the chemical changes induced by alteration. …
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Evidence for rapid epithermal mineralization and coeval bimodal volcanism, Bruner Au-Ag property, NV USA
… two generations of Miocene high-K, high-silica rhyolite flow dome complexes overlying an andesite flow unit. The most prominent structural controls on veining are Nstriking faults and syn-mineral basalt/rhyolite dikes. Productive veins have robust boiling indicators (high adularia content, …
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Evolution of a small silicic system: The McCullough Pass Caldera, Clark County, Nevada
… formed by the eruption of the McCullough Pass rhyolites. The McCullough Pass rhyolites erupted as three successive rhyolitic magma batches from 14.12 to 13.98 Ma and produced the McCullough Pass caldera. Each magma batch was chemically zoned by sidewall crystallization prior to erupting. The …
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Volcanic framework and geochemical evolution of the Archean Hope Bay Greenstone Belt, Nunavut, Canada
… also divided into three main groups, tholeiitic rhyolite, calc-alkaline dacite and calc-alkaline rhyolite groups. Nd and Hf isotope signatures are consistent with trace element signatures in identifying mafic and felsic volcanic groups, with the tholeiitic rhyolite showing highly variable …
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The geochronology and geochemistry of Karoo volcanics in the Lebombo and adjacent areas
… in Swaziland and the southern Lebombo. The rhyolites are notably thinner to the north of Swaziland and are overlain by an upper sequence of olivine-poor lavas with interdigitated rhyolite flows. Basic dykes are ubiquitous in the Lebombo whereas acid dykes, though present, tend to be …
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Structural Analysis of the Northwest Wind Mountain Quadrangle, New Mexico: Proterozoic Shearing to Cenozoic Brittle Faulting in the Burro Mountains
… margin; 2) ~1.4 Ga intrusion of Granite and Rhyolite Province granitoids; 3) significant uplift during the formation of the Ancestral Rockies (~300 Ma) and the Rocky Mountains (~70-50 Ma); and 4) inversion tectonics with reactivation of compressional faults as normal and strike-slip faults …
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