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.
Grain shapes in this thin section tend to be subhedral to anhedral with a great variety in grain size. Lath-shaped plagioclase grains have both albite and Carlsbad twins, while larger, more equant grains show concentric zoning. Other phases in this sample include strongly pleochroic biotite, clinopyroxene, nephaline, orthoclase, and opaques. The clinopyroxene, biotite, and opaques tend to cluster together. Fairly large, euhedral apatite crystals are found throughout.
The bulk of this thin section is augite. In plane polarized light, these grains have pleochroic rims of differing composition, which translates to concentric zoning in cross-polarized light. Twinning is common, as is alteration to a mixture of chlorite and biotite, and the formation of glomeroporphyroclasts. Chlorite and biotite also are found rimming olivine grains, which are themselves clustered with augite and biotite crystals. The mafic phases are typically subhedral in shape, in contrast to the nephaline, k-feldspar, and zeolites which are anhedrally intergrown together in the interstices between augite crystals.
This coarse-grained dacite has a granitic texture of hypidiomorphic inequigranular plagioclase, hornblende, and augite. Secondary zeolites and calcite are found randomly throughout. This thin section is both too thick and plucking is disruptive of many hornblende grains.
Clinopyroxene and plagioclase crystals with a hypidiomorphic granular texture. Clinopyroxene is cloudy and patchy in appearance due to alteration by a fine-grained material. Alteration by randomly-oriented, feathery chlorite pervades grain boundaries and fractures in the thin section.
This blueschist consists mostly of aligned glaucophane, micas, and sphene. Occasional inclusion-rich porphyroclasts of nephaline are observed.
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.
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.
The feldspars in this thin section are partially sericitized and somewhat poikilitic and the biotite is substantially altered. Grains are generally anhedral in shape.
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.
Large k-feldspar and quartz crystals provide a backdrop for the smaller, less well-preserved mafic phases in this sample. Decomposing biotite is frequently found interfingered with chlorite. Hornblende grains are rather skeletal. Plagioclase crystals have relatively rounded corners and tend to cluster together. Large anhedral aggregates of sphene are interspersed in the interstices between k-feldspar grains.
Several glomeroporphyroblasts of clinopyroxene and opaques with hornblende, biotite, and chlorite rims are scattered throughout this syenite. The remainder consists of altered k-feldspars and rare quartz grains with rather sutured grain boundaries.
The predominant mineral in this thin section is opaque red chert which is cross-cut by veins infilled with chlorite and serpentine. Towards the margins of the thin section is a metamorphosed basalt with a groundmass plagioclase mircolites and quartz, calcite, and chlorite in-filled vesicles and veins. According to collector David Sawyer, the interpillow red chert is an important indicator of deep sea origins.
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.
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.
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.
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.
This thin section contains two distinct populations. The background 'matrix' consists of seriate-interlobate feldspar and quartz, with both phases exhibiting microstructures indicative of strain. A decussate fabric of biotite, chlorite, kyanite, and opaques are distributed in pods throughout the quartz and feldspar 'matrix'. Close examination of these pods reveals poikiloblastic host mineral, presumably k-feldspar, which is almost entirely obscured by inclusions. Zircons with radiation halos are extensive within this poikilobastic phase.
Poorly-sorted, angular, clast-supported, arkosic conglomerate with large clasts of deformed quartz and microcline. Many feldspar grains are altering to clays. Deformed micas are interspersed throughout. Perthite and scotch-plaid twins are extensive. The cement is comprised of microcrystalline quartz and locally, calcite.
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.
The most noteworthy feature in this thin section is the micrographic intergrowth between quartz and k-feldspar that pervades the rock. The k-feldspar is dirty in appearance due to alteration to clay. Biotite, which is interfingered with chlorite, is subhedral to anhedral and riddled with inclusions.
The foliation in this rock is defined by aligned lawsonite, chlorite, glaucophane, and calcite. Lenses of quartz are rare. Euhedral though skeletal garnets have overgrown the foliation, and inclusions within the garnet are often continuous with though at an angle to the dominant foliation indicating garnet growth during deformation. This thin section has a greasy-looking film on the surface that makes it difficult to focus clearly.
The largest crystals in this sample are augite, in which twinning is common, as is alteration to a mixture of chlorite and biotite, and the formation of glomeroporphyroclasts. Chlorite and biotite also are found rimming olivine grains, which are themselves clustered with augite and biotite crystals. The mafic phases are typically subhedral in shape, in contrast to the nephaline, k-feldspar, and zeolites which are anhedrally intergrown together in the interstices between augite crystals.
This hypidiomorphic, equigranular monazite has a classic granitic texture with a mosaic of grains all crystallizing simultaneously and impinging on one another's growth. Hornblende is particularly abundant and generally in contact with some combination of biotite, chlorite, and opaques. Some plagioclase grains are concentrically zoned.
This fine-grained granite has a mosaic texture. The quartz seems undisturbed, however, most other phases display evidence of weathering and disequilibrium. The dusting of clays and presence of sericite inclusions in the feldspars indicates they are chemically weathered. Biotite and muscovite are skeletal in appearance and biotite is frequently interfingered with chlorite.