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.
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.
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.
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.
The phenocrysts in this porphyritic granite are inclusion-rich, clay-altered, subhedral plagioclase blocks that do not appear to be in equilibrium with the surrounding groundmass. The groundmass is a mottled smattering of quartzofeldspathic minerals that have no discernable crystal habit. Amidst the background blur of first-order whites and grays are petrographically messy clusters of chlorite, hornblende, and iddingsite, with growth of chlorite and iddingsite at the expense of hornblende. Large, prismatic and hexagonal apatite crystals are readily apparent in this thin section. A few prismatic crystals of monazite, zircon, or xenotime are present (though difficult to definitively identify).
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 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.
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.
Strongly aligned actinolite crystals define a strongly folded foliation with lenses of subparallel chlorite crystals.
A very poorly sorted rock with variably sized and angular quartz and feldspar pieces (both plagioclase and orthoclase; some fresh, others sericitized) set in a finer-grained matrix of chlorite, sericite, carbonate, silky quartz, leucoxene, magnetite and pyrite. Matrix chlorite corrodes quartz grains marginally. A few microfragments of rock (quartzite, granite, gneiss) also are present. Accessory detritals include muscovite, sphene, tourmaline and epidote. Most of the quartz pieces are markedly undulatory. A very low degree of incipient metamorphism is indicated by abundant secondary epidote in the matrix which also locally contains minute platelets of stilpnomelane.
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.
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.
This sample has a granitic texture and contains roughly equal amounts of both feldspar phases. The k-feldspars are more sericitized than the plagioclase grains, many of which are concentrically zoned. The hornblende grains are anhedral and a times, form almost granular aggregates of equant grains. Hornblende is altering to chlorite, which also interfingers with the relatively subhedral biotite phase. Apatite and epidote are present in trace amounts.
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.
According to the sample information sheet, JPN-21 is a crossite-epidote-amphibole-bearing blueschist. Though mineral identification is somewhat complicated by the fine-grained nature of this foliated green rock, the dominant minerals appear to be quartz, chlorite, and calcite or aragonite, all of which are elongated and strongly aligned.
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.
Like the other blueschists, aligned glaucophane, clinozoisite, and sphene define the foliation, however, this sample lacks omphacite and garnet, and contains quartz and aragonite instead. These latter two phases are interstitial and occur in minor amounts,
The fabric in this thin section is more disordered than others from this suite. All phases commingle and an alignment of elongate phases amidst many equant phase forms a weak foliation. Garnet and omphacite form porphryclastic, poikiloblastic grains.
This gabbro has a subophitic texture. Alteration to chlorite and iddingsite occurs mostly between grain boundaries.
This blueschist consists mostly of aligned glaucophane, micas, and sphene. Occasional inclusion-rich porphyroclasts of nephaline are observed.
This rock grades from an omphacite-rich zone into a muscovite-rich zone, and yet again into a glaucophane and chlorite-rich zone. The transitions between each section is rather abrupt. Micaceous phases are strongly aligned to define a foliation. Sphene is noticeably less abundant than in other samples. A k-feldspar porphyroclast surrounded by radiating chlorite is observed in the chlorite-glaucophane region.
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 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.