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66 hits

  • Thumbnail for ERB-23
    ERB-23

    Intergrown, subhedral two-pyroxene gabbro with hornblende and poikilitic plagiclase with deformation twins and abundant pyroxene inclusions.

  • Thumbnail for ERB-09a
    ERB-09a

    Grain boundaries between the quartz and feldspar phases in this sample are consistently lobate, often with finer-grained subgrains rimming each crystal. Quartz in undulatory. The mica phases are subhedral and often resorbed, with kink bands causing undulose extinction along the length of the grain. Along one edge of the thin section is a seam dominated by clinozoisite. A hematite stain gives a dusty orange appearance to the feldspars and fractures within the sample contain higher concentrations of the phase.

  • Thumbnail for ERB-09b
    ERB-09b

    This metamorphosed granite has a weak spaced foliation defined by moderately aligned elongate minerals and slight compositional layering. The opaque phases are segregated into two discrete bands, along which, large quartz grains show a crystallographically preferred orientation, causing them to appear nearly isotropic. Alternatively, this nearly isotropic phase could be untwinned leucite, however, an the lack of twins and association with the remaining phases is unlikely. The chlorite and muscovite phases appear to be collectively pseudomorphing a preexisting phase, as evidenced by dark, elongate inclusions within the chlorite grains.

  • 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 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 ERB-0X3
    ERB-0X3

    In this sample, a spaced, anastamosing schistoscity defined by biotite, garnet, hornblende and opaques wraps around deformed feldspar lenses which display undulose extinction and bent growth as well as deformation twins. Polyganized quartz and feldspar mantles the feldspar porphyroclasts. Quartz ribbons are prevalent throughout this sample. The sense of shear is ambiguous.

  • Thumbnail for SYH-3D-2
    SYH-3D-2

    This thin section consists of several zones. The first, a fine-grained glaucophane schist. The boundaries between individual glaucophane crystals frequently blur. Aggregates of sphene are stretched out lines paralleling the complexly folded foliation. This zone is abruptly cut by a green, omphacite-rich band, bordered on each sided by a greater concentration of sphene. In the third zone, the glaucophane fabric is interleaved with elongate aggregates of omphacite, epidote and sphene.

  • Thumbnail for SYH-1D-2
    SYH-1D-2

    Glaucophane, muscovite, sphene, and elongate aggregates of epidote-group minerals define the foliation in this thin section. Poikiloblastic garnet and omphacite grains contain inclusions which include glaucophane and rutile and the host minerals show resorption textures.

  • Thumbnail for SYH-1R
    SYH-1R

    Aligned, elongate, millimetric-scale actinolite crystals dominate this thin section. Layers of actinolite crystals are interleaved with layers of chlorite. Basal sections of actinolite, which show fabulous amphibole cleavage are strongly plucked, leaving patchy void spaces throughout the thin section.

  • Thumbnail for ERB-02
    ERB-02

    This sample is a strongly mylonitized pelitic schist with a continuous schistoscity defined by strongly alligned biotite, fibrous sillimanite, and opaques and interspersed with discontinuous quartz and k-feldspar ribbons. K-feldspar is strongly sericitized. The sense of shear is ambiguous.

  • 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 Ralph
    Ralph

    Large, interlocking calcite crystals comprise this marble. This thin section is useful for finding interference figures.

  • Thumbnail for ERB-03
    ERB-03

    In this mylonitized sample, biotite, sillimanite, and the opaques define a spaced schistoscity overprinting a background matrix of seriate-interlobate quartz and feldspar. The foliation wraps around polymineralic porphyroclasts with fish-like shapes. The sense of shear is ambiguous. A lineation is defined by aligned sillimanite and biotite.

  • 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 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 23-6
    23-6

    This amphibolite has a strong, continuous foliation defined by the alignment of hornblende. Elongate, granular aggregates of epidote 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 SYH-1FF
    SYH-1FF

    This blueschist consists mostly of aligned glaucophane, micas, and sphene. Occasional inclusion-rich porphyroclasts of nephaline are observed.

  • Thumbnail for SYH-1EE
    SYH-1EE

    Allotriomorphic omphacite and clinozoisite are intergrown with one another, with clinozoisite occurring frequently as inclusions within the omphacite crystals. The occurrence of muscovite is typically contained to polycrystalline nodes with radiating crystals. The conspicuous rutile grain in the center with radiating veinlets has a rim of plagioclase buffering it from the surrounding material. It contains inclusions of chlorite and sphene. Sphene is abundant as large, subhedral clasts.

  • Thumbnail for AMA004E
    AMA004E

    The elongate minerals, glaucophane, clinozoisite and muscovite define the foliation in this sample, which is tightly folded in a crenulation cleavage.

  • Thumbnail for GR-07
    GR-07

    Aligned muscovite crystals form a foliation with anhedral, interlobate, though elongated grains of quartz and k-feldspar. Grain boundaries are irregularly shaped.

  • Thumbnail for GR-11
    GR-11

    Stacked, elongate, monocrystalline calcite layers.

  • Thumbnail for 74
    74

    Composed mainly of a variably textured aggregate of antigorite and talc. Some parts are mainly fine interlaces of serpentine; others consist of both serpentine and talc completely intertwined and still other parts are mainly talcose. Veinlets and bands of these minerals, together with some carbonate are widespread. There is also considerable carbonate which appears in two types of two distinct ages 1) corroded patches of an older turbid carbonate and 2) veinlets of a younger, clear magnesite. Streaks and patches of fine-grained magnetite are common throughout.

  • 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 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.