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123 hits

  • Thumbnail for 884
    884

    The flame lamellae that pervade this thin section are cut thicker than ususal and thus display first order yellows and oranges, though the tartan twinning of the microcline retains the ususal first order grey birefringence. Grain boundaries between feldspars are lined with smaller feldspar grains, which gives the larger grains a scalloped appearance. The hornblende grains are highly irregular in shape and contain many inclusions of feldspar, opaques, biotite, and other unidentifiable phases.

  • Thumbnail for 878
    878

    Grain shapes in this thin section are consistantly anhedral. Weathering of the feldspars give them a dusty appearance. Because the thin section is cut too thick, the birefringence of quartz and some k-feldspars is as high as second order blues. Mnay hornblende crystals are nearly opaque and they are frequently found surrounding and likely replacing inclusions of pyroxene (perhaps). The biotite and hornblende are rather skeletal. Euhedral sphene and apatite are occasionally scattered throughout.

  • Thumbnail for 877
    877

    This generally allotriomprhic-equigranular thin section is thicker than standar thin sections, thus the quartz and some k-feldspar grains display first order red to pink colors. The riebeckite is nearly opaque in both plane and cross-polarized light.

  • Thumbnail for BB18
    BB18

    This fine-grained granite contains abundant feldspars, many of which display concentric zoning from plagioclase cores to k-feldspar rims. Biotite grains are altering to and interfingered with chlorite. Rounded hornblende crystals are rare in this sample.

  • Thumbnail for 872
    872

    The feldspar grains in this thin section span a broad range of sizes, with larger grains displaying strong lamellae of either the blebby or flame variety. The mafic phases are anhedral to skeletal in shape and are much less abundant than the more felsic phases. The minerals in this thin section are highly fractured lending the appearance of porousness to this intrusive igneous rock.

  • Thumbnail for 513
    513

    Square phenocrysts of quartz and feldspar disrupt this porphyritic granite's otherwise mosaic of equigranular grains. Subhedral and partially resorbed biotite is scattered throughout.

  • Thumbnail for 544
    544

    Although the bulk of this thin section has an aplitic texture of quartz and feldspar, several larger feldspar phenocrysts punctuate the mosaic texture of the smaller population of quartzofeldspathic phases. Biotite is sparse and where present, skeletal in shape.

  • Thumbnail for 22
    22

    Most phases in this thin section are subhedral to anhedral in shape. The k-feldspar have patchy exsolution textures. Most other phases are sparsely distributed and generally subhedral to anhedral.

  • Thumbnail for SS-3
    SS-3

    This coarse-grained sample contains phenocrysts of a wide variety of size and composition. The largest, visible in hand sample as whitish spheres with obvious rims, are intergrown, wedge-shaped k-feldspars and radiating blades of natrolite. A dusting of sericite throughout the k-feldspar gives a cloudy appearance to the these mineral aggregates. Randomly oriented grains of these same phases comprise the bulk of the 'groundmass' for this sample. Augite phenocrysts are the dominant mafic phase and display a variable degree of alteration to iddingsite?. A few grains of arfvedsonite can be seen associated with the pyroxenes.

  • Thumbnail for SS-6
    SS-6

    Most noteworthy in this sample are the millimeter-scale, euhedral, augite crystals with compositional zoning, twinning, more magnesian rims. Biotite is the subhedral phenocrystic phase in this sample and both are surrounded by interstitial nephaline. Several nephaline grains display micrographic-like intergrowths with a cloudy, difficult to identify phase. Equant olivine grains are frequently found as inclusions within pyroxene and biotite phenocrysts. Euhedral apatite are found throughout.

  • Thumbnail for B[m+s]
    B[m+s]

    The outer rim of this bomb is glassy with vesicles and augite and olivine phenocrysts. Small, widely dispersed plagioclase microlites are also present. The core of the bomb contains a porous aggregate of fragmental quartz held together by glass.

  • Thumbnail for PS-2d-troc
    PS-2d-troc

    Allotriomorphic plagioclase and highly-fractured olivine are the dominant minerals in this thin section. Clinopyroxene, when present, is found adjacent to olivine. Fractured zones in this rock follow olivine clusters and frequently cross-cut plagioclase crystals in swarms between nodes of granular olivine.

  • Thumbnail for PS-2c-lg
    PS-2c-lg

    Granular, inequigranular gabbro containing occasional olivine crystals. Serpentine is localized to fractures. Grain shapes are very rounded and amorphous.

  • Thumbnail for SW6
    SW6

    Large, anhedral, interlocking crystals of olivine and clinopyroxene are found in this coarse-grained rock. Olivine alteration to iddinsite is confined to fractures which pervade the rock and cross-cut both mineral phases. Perthitic pyroxene intergrowths are observed. A contact between an ore-rich, opaque zone and the peridotite is preserved in the thin section.

  • Thumbnail for 868
    868

    The coarseness of this granite obscures in thin section the graphic texture so evident in handsample. The feldspars contain inclusions of muscovite as well as zircon (or another like mineral) and untwinned grains are readily distinguished from quartz by the comprehensive dusting of clay minerals due to weathering.

  • Thumbnail for SW10
    SW10

    This coarse-grained sample consists of large, euhedral, often twinned clinopyroxene crystals. Alteration along cracks contains minor chlorite.

  • Thumbnail for KBR9
    KBR9

    Plagioclase and clinopyroxene form subhedral and anhedral grains, respectively, though unlike the other ferrotholeiites in this suite, both are cross-cut by or being pseudomorphed by iddingsite, a very dominant mineral in this thin section. Interstitial, undeformed quartz is found in the groundmass and inclusions of apatite crystals lend an almost graphic texture to this phase. Described by Western Minerals Inc. as an 'interstitial ferrotholeiite, very highly fractionated…textures are similar to those associated with rapidly frozen or highly viscous melts.'

  • Thumbnail for KBR11
    KBR11

    Like KRB10, plagioclase and clinopyroxene are intergrown in an almost graphic texture, though where KRB10 was dominated by the unknown mineral, in KRB11, that unknown mineral is confined to spherulite-like clusters in a fine-grained quartz matrix. Iddingsite alteration is much less extensive. Western Minerals Inc. as an 'interstitial ferrotholeiite, very highly fractionated…textures are similar to those associated with rapidly frozen or highly viscous melts.'

  • Thumbnail for CM4
    CM4

    The vesicles in this microporphyritic vesicular basalt are substantially smaller than the other Carr Mountain samples, though composition remains similar. More calcite permeates the groundmass, in which plagioclase microlites are visible. Unaltered augite and olivine microphenocrysts are observed. An isotropic zeolite, presumably analcite, is seen infilling several vesicles.

  • Thumbnail for SG1A
    SG1A

    Plagioclase laths of varying sizes and orientations represent the bulk of this thin section. Augite is present, though in noticeably smaller quantities and olivine only in trace amounts. Tiny opaques pervade the sample.

  • Thumbnail for KBR12
    KBR12

    Described by Western Minerals Inc. as 'porphyroblastic metasediments/hybrid rocks, interpreted by Eales and his coworkers as metamorphosed 'Red Beds' Formation sediments but conceivably magmatic in origin. The specimens illustrate the range in textures and compositions.' If so, textures in this sample, though difficult to describe, better resemble those of igneous than sedimentary rocks. This sample is jumbled mess of bladed, graphically intergrown k-feldspar and clinopyroxene, subhedral plagioclase altering to a dendritic, cloudy mineral, patches of anhedral, granular quartz, and elongate, poikilitic opaques.

  • Thumbnail for 1059
    1059

    This sample consists of two distinct populations distinguished by size and composition. The groundmass of elongate subhedral crystals of plagioclase, orthopyroxene and opaques is interspersed with vesicles infilled with calcite. The calcite amygdules are rimmed with quartz and occasionally chlorite.

  • Thumbnail for 875
    875

    The quartz and feldspar grains in this thin section have rather amoeboid, though elongated shapes. These elongated grains are roughly aligned giving this syenite a somewhat layered appearance. Feldspar intergrowths are primarily of the flame lamellae variety. Rare biotite grains are observed.

  • Thumbnail for 865
    865

    A noteworthy characteristic of this allotriomorphic granite is the presence of feldspar laths with albite twinning in the core and anhedral k-feldspar rims. The remainder of the rock is comprised of equigranular and subhedral biotite, hornblende, and k-feldspar grains. Randomly oriented prismatic apatite grains are abundant in this sample.

  • Thumbnail for unknown-71
    unknown-71

    Unaligned, prismatic crystals of schorl, with strongly mauve to indigo pleochroism and concentric compositional zoning are scattered throughout the sample. Basal sections remain a deep blue regardless of rotation of the stage. A corona of clear tourmaline (perhaps) rims most grains. The tourmaline are found in a sericitized feldspars.