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20 hits

  • Thumbnail for KBR5
    KBR5

    Plagioclase is roughly twice as abundant than clinopyroxene in this sample, though where present, clinopyroxene grains are large and encompass multiple inclusions of plagioclase giving a spotty ophitic texture to the gabbro. Iddingsite replacement is extensive and plagioclase is altering to clays. Apatite is found in short stubby prisms, hexagonal cross sections, and long needles.

  • Thumbnail for KBR4
    KBR4

    Plagioclase and clinopyroxene abundances are lower in this gabbro compared to others of Birds River. Radiating splays of zeolites with serpentinized margins, as well as iddingsite and chlorite replacement of an equant mineral phase contributes nearly half the bulk of the thin section.

  • 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 KBR8
    KBR8

    Plagioclase and clinopyroxene form subhedral, unaltered grains amongst a background of finer-grained, intermingled iddingsite and zeolites. Iddingsite may be a pseudomorph after biotite. 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 KBR6
    KBR6

    Though clinopyroxene and plagioclase were undoubtedly once more abundant in this gabbro, subsequent alteration has left radiating zeolites, a cloudy film of clays, and veinlets and pseudomorphs of iddingsite the dominant minerals in this thin section.

  • Thumbnail for KBR13
    KBR13

    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.' Texturally, this fine-grained thin section is an allotriomorphic, junky intergrowth of larger, roughly rectangular feldspars with granular calcite and chlorite. Opaques are abundant.

  • Thumbnail for KBR3
    KBR3

    The clinopyroxene abundance in this thin section is lower than other gabbros from Birds River, lending more of a subophitic texture to the rock. Plagioclase is the most dominant mineral. Iddingsite is less abundant.

  • Thumbnail for KBR2A
    KBR2A

    This gabbro has a subophitic texture. Alteration to chlorite and iddingsite occurs mostly between grain boundaries.

  • 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 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 KBR2
    KBR2

    The dominant texture in this gabbro is an ophitic intergrowth of equant plagioclase laths within larger, subhedral, clinopyroxene grains. Alteration of some phases to chlorite, talc and iddingsite is localized and occurs more in non-ophitic sections of the rock.

  • Thumbnail for KBR1
    KBR1

    The dominant texture in this gabbro is an ophitic intergrowth of equant plagioclase laths within larger, subhedral, clinopyroxene grains. Alteration of some phases to chlorite, talc and clays is localized and occurs more in non-ophitic sections of the rock.

  • Thumbnail for KBR18
    KBR18

    Elongate plagioclase laths with interstitial clinopyroxene and minor interstitial hornblende and biotite. Classic diabasic texture. Said by Western Minerals Inc. to be the youngest dolerite body in the area and was emplaced at much deeper crustal levels than the gabbros.

  • Thumbnail for KBR14
    KBR14

    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.' A common characteristic of all minerals in this thin section is that despite their natural habit, most minerals are elongate and frequently form cross-cutting, disparate but optically continuous, bladed crystals. It appears to be an almost dendritic intergrowth of all phases.

  • Thumbnail for KBR7
    KBR7

    Plagioclase and clinopyroxene form subhedral, unaltered grains amongst a background of finer-grained, intermingled iddingsite and zeolites. 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 KBR19
    KBR19

    Fragmental quartz chunks in glass with occasional glass-surrounded plagioclase clusters. Western Minerals Inc. indicates this sample has partially melted to glass with tridymite developed.

  • Thumbnail for KBR10
    KBR10

    The unknown mineral is the prominent mineral in this thin section. It forms a dusty brown, isotropic matrix with a faint dendritic texture in which subhedral clinopyroxene and plagioclase grains are set. Clinopyroxene, where isolated, is strongly altered to iddingsite. The degree of alteration is much lower where plagioclase and clinopyroxene grains are intergrown. The two minerals have an almost graphic intergrowth texture. 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 KBR15
    KBR15

    According to Western Minerals Inc., this sample is a 'contact rock from sediment immediately above dolerite,…rock with quartz 'spots'–probably inverted from tridymite spherulites–in a matrix of devitrified glass with mullite and cordierite.' Due to the fine-grained nature of the sample, it is difficult to distinguish individual mineral phases in the allotriomorphic, equigranular, microcrystalline groundmass. The only noteworthy features in this thin section are the spherical, slightly coarser grained nodules with orange-brown rims.

  • Thumbnail for KBR16
    KBR16

    This thin section is noticeably layered with alternating lenticular zones of compositionally similar quartzofeldspathic layers of differing grain size. Plagioclase, k-feldspar, quartz and glass or clay are the identifiable mineral phases. This is described by Western Minerals Inc. as 'adinole, potassium-rich, with ?hercynite. From same type of situation as KRB15...Occurs above a conspicuous dolerite pegmatite.'

  • Thumbnail for KBR17
    KBR17

    Western Minerals Inc. calls this sample as 'metasomatised pyroclastics, baked and well indurated, slightly metasomatised.' It is fine-grained and dominated by anhedral quartzofeldspathic phases which vary in size and are peppered with small, equant pyroxenes. Rounded, partially chloritized clusters are scattered throughout.