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15 hits

  • Thumbnail for J-26-11C
    J-26-11C

    This strongly foliated sample contains mostly hornblende crystals, the alignement of which defines the schistoscity. A granoblastic texture consisting of quartz, and highly poikiolblastic k-feldspar is interspersed among the hornblende grains. Occasional subhedral epidote and calcite grains crop up through the thin section. Of special note are a series of fractures that obliquely cross-cut the foliation; cataclastic textures can be observed along these zones. Small, rounded, colorless to light brown titanite crystals are present.

  • Thumbnail for 25-2
    25-2

    The hornblende crystals in this thin section are prismatic and subhedral to euhedral in shape. They are strongly aligned. Filling in between the amphiboles are altered feldspars, granular epidote crystals and euhedral apatites.

  • Thumbnail for 23-3A
    23-3A

    This strongly foliated amphibolite shows evidence of mimetic growth of k-feldspar into elongate crystals due to restriction of a preexisting fabric defined by amphibole and micas. The dominant mica phase, chlorite, has anhedral (almost skeletal) grain shapes. Hornblende is the same. Both phases are highly embayed. Several hornblende grains contain euhedral feldspar 'inclusions' and the classic amphibole grain shape is lost along its margins due to encroaching feldspar grains. Chlorite tends to be associated with elongate epidote crystals or granular aggregates. Dusty fracture zones trace across the fabric of this sample and are filled with cataclastic breccia and glass. Euhedral apatite and small, rounded to larger, anhedral titanite grains are dispersed throughout the thin section, typically oriented with the foliation.

  • Thumbnail for A-18-6B
    A-18-6B

    The subhedral hornblende crystals in the sample align with the micas to form a spaced foliation separating microlithons of plagioclase and quartz. Equant subhedral epidote crystals punctuate the rock. Biotite and chlorite are typically interfingered and chlorite display anomalous blue interference colors. Elongate granular aggregates of light brown to colorless titanite are present.

  • Thumbnail for 23-5A
    23-5A

    A continuous foliation defined by aligned euhedral biotite characterizes this fine-grained sample. Granoblastic quartz and feldspars fill the voids between biotite crystals. Small, equant opaqes are distributed evenly throughout.

  • Thumbnail for A-6-7
    A-6-7

    A continuous foliation for this sample is defined by aligned hornblende, micas, elongate quartz grains and granular aggregates of epidote and clinozoisite. Quartz is either equant or elongate with a granular texture. The hornblende phase is generally subhedral in shape, as are biotite crystals, which appear to be pseudomorphing an earlier mineral phase as evidenced by abundant inclusions. Radiation halos can be found in this sample though their occurrance is rare.

  • Thumbnail for 21-4
    21-4

    The foliation in this coarse-grained rock is the result of compositional layering; discontinuous hornblende-rich zones separate poikiloblastic plagioclase-rich regions. Albite and Carlsbad twins in the feldspars are almost entirely obscured by randomly-oriented inclusions of sericite.

  • Thumbnail for 18-9
    18-9

    The layering in this fine-grained amphibolites is defined by bands of amphibole alternating with granoblastic quartzofeldspathic layers. Granular aggregates of epidote are dispersed randomly throughout the rock. Fractures cross-cutting and off-setting the layering are more visible with the naked eye then under the microscope, though one fracture (with no offset) is filled with a seam of epidote. A couple of porphyroclastic and poikiloblastic chlorite grains are clearly truncated by the fractures.

  • Thumbnail for 23-6K
    23-6K

    A foliation defined by aligned hornblende is cross-cut by a seam running from the upper-left to lower-right of the thin section. The seam is coarse-grained and unfoliated with a quartzofeldspathic margin and grains of resorbed, subhedral clinopyroxene in the middle.

  • Thumbnail for 23-3B
    23-3B

    This unfoliated sample contains randomly oriented, subhedral hornblende, with large poikiloblastic and deformed chlorite clasts. The matrix of this thin section is predominately poikiloblastic feldspar with occasional calcite crystals. Embayed chlorite grains are found with aligned inclusions of epidote, calcite, and feldspar.

  • Thumbnail for 21-1B
    21-1B

    The foliation in this sample is due in part to aligned hornblende crystals and also to a slight compositional layering. The hornblende grains concentrate in layers of larger grains, with smaller, less abundant layers dominated more by granoblastic quartzofeldspathic phases. Lenticular layers of inclusions within the quartzofeldspathic layers lend a cloudy appearance to portion of the rock. Larger grains of epidote are evident by their classic yellowy-green pleochroism. Small, rounded, colorless titanite crystals are found throughout.

  • Thumbnail for A-6-8B
    A-6-8B

    This sample is an almost monomineralic hornblende amphibolite with trace occurances of poikiloblastic orthoclase and biotite. Biotite growth concentrates along the margins of a high relief, clear mineral with fifth-order birefringence, extreme enough that the inclusions appear to not go extinct. Rarely are radiaiton halos observed in hornblende crystals.

  • Thumbnail for 27-2A
    27-2A

    A continuous foliation in this sample is defined by aligned hornblende grains. Altered biotites are poikiloblastic and have kink bands causing undulose extinction. The aligned hornblende grains are juxtaposed against equigranular polygonal-interlobate quartz and aggregates of altered and decussate muscovite and clinozoisite.

  • Thumbnail for J-9-4
    J-9-4

    Strongly aligned hornblende grains define a continuous foliaiton in this thin section. Interspersed among these grains are polygonal quartz and fine-grained aggregates of clinozoisite and anhedral muscovite.

  • Thumbnail for 23-6
    23-6

    This amphibolite has a strong, continuous foliation defined by the alignment of hornblende. Elongate, granular aggregates of epidote are present.