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Showing 1 to 20 of 79 for “"hornblende"”.
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The Hornblende-Aegirine Augite Reaction Relationships of the Trunk Lake Granite, Maine
… augite controlled the secondary formation of hornblende in the Tunk Lake granite. In the marginal rocks of the granite body some grains of aegirine augite may be partially or completely enclosed by hornblende. Hornblende also replaces aegirine augite along fractures. Extensive replacement …
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Petrogenesis of the Springfield Granodiorite, southeast Pennsylvania Piedmont
… (often with allanite cores) and trace amounts of hornblende. Accessory minerals include sphene, magnetite, apatite and zircon. The magmatic assemblage of quartz+two feldspars+biotite+sphene+hornblende+magnetite permits its utilization of AI-in-hornblende as a geobarometer (Schmidt, 1992) and …
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Heavy minerals of glacial sediments in the area of Red Lake Falls, Minnesota
… diffraction methods. Most formations contain a hornblende-garnet-pyroxene-epidote assemblage; the Gervais Formation contains a pyroxene-hornblende assemblage. The mean proportion of the constituent minerals is different in each formation; however, there is overlap in the ranges of heavy mineral …
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Petrogenesis of the Moosehorn igneous complex, Maine
… intruded by slightly peraluminous biotite ± hornblende granites as demonstrated by the occurrence of a wide range of enclave-host relationships. The igneous complexes are commonly cut by younger voluminous biotite ± hornblende granites and represent the development of a new tectonothermal …
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Petrology and contact relationships, SW portion PC Mullen Creek mafic complex, Medicine Bow Mts., Wy.
… invaded a metavolcanic sequence (predominantly hornblende gneiss). This portion of the mafic complex consists of variably metamorphosed interlayered rocks that originally ranged from pyroxenite to anorthosite but were dominantly gabbro and leucogabbro. Most of these rocks underwent regional …
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The interaction between chemical and mechanical processes during metamorphism: a microstructural and petrologic study of amphibolite shear zones, Cheyenne Belt, Southeastern Wyoming
… Amphibole compositions vary from actinolitic hornblende to magnesio-hornblende which involves increases in Al, Fe, Na and K contents and decreases in Si and Mg. Plagioclase compositions vary from Angp in cores of plagioclase grains to Anjo within grain boundary domains. With increasing strain …
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A stable isotope study of the Kaap Valley Tonalite, Barberton Mountain Land, South Africa
The Kaap Valley Tonalite (KVT) was a homogenous hornblende+ biotite tonalite that had been subjected to overail propylitic and potassic alteration. Petrographic studies reveal that carbonate alteration and increased proportions of hydrous minerals occur along the KVT and Barberton greenstone belt …
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Antarctica's Geologic and Ice Sheet History from Isotopic Sedimentary Provenance Studies
… isotopic measurements - 40Ar/39Ar on detrital hornblende and biotite grains, U-Pb on detrital zircons. I have also employed Nd isotope measurements on the terrigenous fine (< 63µm) fractions of these same samples. Chapter 2 is published in the journal Paleoceanography, and chapters 3 and 4 are …
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Hydrophobic Forces in Flotation
… include covellite (CuS), sphalerite (ZnS) and hornblende (Ca₂(Mg, Fe)₅(Si₈O₂₂)(OH,F)₂). The collector used for all the mineral systems studied was potassium ethyl xanthate (KEX). For the covellite-xanthate system, a biopotentiostat was used in conjunction with the AFM to control the potential …
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Petrology of the Numabin Bay intrusions, Reindeer Lake, Saskatchewan
… plagioclase and in the amounts of plagioclase, hornblende,and biotite; (2) an increase in the percentage of K feldspar; and (3) no consistent variation in the proportion of quartz towards the core of the pluton. Textures and microstructures show that early-formed minerals underwent cataclasis …
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Petrogenesis of a migmatite, Penobscot County, Maine: ultrametamorphism or intrusion?
… The leucosomes are I-type (metaluminous, hornblendebearing inclusions, primary titanite, allanite, hornblende, and apatite included in biotite or hornblende), or S-type (tourmaline and red-brown biotite). They are conformable with melanosome (Bucksport) layering, and vary in outcrop from …
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A chemical study of the silicate minerals of the Great Gossen Lead and surrounding rocks in southwestern Virginia
… Other lithologies include thin layers of hornblende amphibolite, sulfide ore, quartz veins, thin layers of hornblendic gneiss, marble lenses and minor solution cavities. The coarser-grained ore zone lithologies are dominated by chlorite, hornblende and actinolite-tremolite with …
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Sedimentology of historic and prehistoric deposits in the drainage basin of Deep River and Muddy Creek on the Piedmont of North Carolina
… show Fe2O3, MnO, TiO2, Al2O3, MgO, epidote, hornblende, and 14 A clays are associated with high magnetic susceptibility in fine-grained historic sediments. Magnetic susceptibility is higher in the interval from fine sand to fine silt in the prehistoric sediments. The magnetic susceptibility …
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The Construction of a Plutonic Complex in a Continental Arc Setting: The Skookum Butte Stock, Western Montana
… granite/granodiorite and biotite-hornblende granite/granodiorite, to subordinate quartz monzodiorite, and monzogabbro. Both field evidence and geochemical data indicate that SBS magmas were generated from at least two distinct sources: a primitive source of mafic to intermediate …
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The Construction of a Plutonic Complex in a Continental Arc Setting: The Skookum Butte Stock, Western Montana
… granite/granodiorite and biotite-hornblende granite/granodiorite, to subordinate quartz monzodiorite, and monzogabbro. Both field evidence and geochemical data indicate that SBS magmas were generated from at least two distinct sources: a primitive source of mafic to intermediate …
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Petrogenesis of the reversely zoned Turtle pluton, Southeastern California
… contribution from entrained basaltic enclaves. Hornblende geobarometry indicates the Turtle pluton crystallized at about 3.5 kb. A crystallization sequence of biotite before hornblende (and lack of pyroxenes) suggests the initial granitic magma contained less than 4 wt% H₂0 at temperatures less …
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Structural-metamorphic imprint on part of the Namaqua mobile belt in Southwest Africa
… which is bounded on the low-grade side by the 'hornblende in' reaction and includes with increasing grade 'muscovite+ chlorite out', andalusite/sillimanite inversion, minimum melt line, •·epidote out', 'K-felspar + sillimanite in' and a brown hornblende zone. The PT conditions inferred for the …
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The petrology and geochemistry of Precaldera Magmas, Long Valley Caldera, Eastern California
… I km³), and (3) sparsely -phyric orthopyroxene -hornblende -plagioclase quartz latite dome-flows and coarsely -phyric biotite -hornblende -plagioclase quartz latite dome-flows ( > 4 km³) erupted in that general sequence. Field, petrographic, and major-, minor-, and trace-element, as well as Sr …
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The petrogenesis and geochemistry of the dioritic complexes south of Balmoral forest, Angus
… 80%) of the succession consists of heterogeneous hornblende- and pyroxene-bearing diorites. Partially assimilated rafted metasedimentary xenoliths, are common in the intermediate rock types. The basic rocks are cumulates which display wall-parallel layering. Mineralogical variation displays a …
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Towards using seismic anisotropy to interpret ductile deformation in mafic lower crust
… stains. The sample suite is characterised as a hornblende-plagioclase-quartz aggregate that develops macroscopic planar and linear fabrics with strain, from an essentially isotropic protolith. Quantification of the aggregate lattice preferred orientation (LPO) using electron backscatter …
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