samples FKM-76 to FKM-100

 

Check out the thin section scans introduction page for more information on the variety of samples featured here, how the scans were taken & processed for web display, and what additional optical and analytical data I hope to include in the figure captions as I continue to update the site and add to the collection of thin sections.

There’s also a fully searchable index covering the complete thin section set, listing for each sample its locality, the anticipated major minerals, a brief generalized geologic environment description, and where appropriate, the nature of any unusual element enrichments.

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sample: FKM-76
locality: Broken Hill, Yancowinna Co., NSW, Australia.
rock type: test.
major mineralogy: inesite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-77
locality: Ilímaussaq complex, Narsaq, Kujalleq, Greenland.
rock type: kakortokite. Cumulate eudialyte-nepheline syenite.
major mineralogy: Eudialyte, arfvedsonite, nepheline, plagioclase.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-78
locality: Bozeman Corundum Company mine, Gallatin Gateway, Gallatin Co., MT, USA.
rock type: test.
major mineralogy: corundum.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-79
locality: Black Rock, Leucite Hills, Sweetwater Co., WY, USA.
rock type: test.
major mineralogy: specimen acquired for fluoro-potassic-richterite, but no amphibole is present in this thin section.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-80
locality: In den Dellen quarry, Niedermendig, Mendig, Laacher See volcanic complex, Eifel, Rhineland-Palatinate, Germany.
rock type: haüyne phonolite.
major mineralogy: Largely sanidine, with scattered haüyne (sparse in this particular thin section and not easily visible in these images), and minor apatite, aegirine, and oxide.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-81
locality: Biesenrode, Wippra metamorphic zone (Wippertal), Harz, Saxony-Anhalt, Germany.
rock type: quartz-carpholite schist. Low-T blueschist facies of original presumably siliceous manganiferous sediment.
major mineralogy: Bands of subparallel carpholite fibers (with local small patches of magnesiocarpholite) intergrown with quartz, minor chlorite (sudoite) and Fe-oxide. Scattered tiny apatite is also present (containing ~450-850 ppm As).
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-81
fluorapatite (Ca4.87Mn2+0.07[M+HREE]0.01)[P3.02Si0.01O12](F0.96[OH]0.04)
carpholite-rich ss (main) (Mn2+0.56Mg0.29Fe2+0.13Fe3+0.01Ti0.01)(Al1.99Fe3+0.01)[Si1.97Al0.03O6]([OH]3.95F0.05)
magnesiocarpholite-rich ss
(sparse patches in main)
(Mg0.48Mn2+0.35Fe2+0.15)Al2.00[Si1.98Al0.02O6]([OH]3.94F0.06)
sudoite (Al2.88Mg1.70FeT0.31MnT0.03Ni0.011.07)[Si3.15Al0.85O10]([OH]7.99F0.01)

 



sample: FKM-82
locality: Itremo commune, Ambatofinandrahana district, Fianarantsoa province, Madagascar.
rock type: test.
major mineralogy: specimen acquired for dumortierite and sillimanite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-83
locality: Långban, Filipstad, Värmland, Sweden.
rock type: test.
major mineralogy: specimen acquired for magnesioferrite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-84
locality: ~3 km SW of Kansi, Hpakant-Tawmaw jade tract, Kachin state, Burma.
rock type: altered jadeitite vein in eckermannite schist. Blueschist facies Na-metasomatite(?)
major mineralogy: The vein envelope portion (upper third of image) is largely Cr-bearing eckermannite, moderately veined with natrolite ± albite. The main jadeite vein center (lower two thirds of image) is composed of scattered Cr-bearing eckermannite, abundant Cr-bearing jadeite, and sparse small bright emerald green kosmochlor, all extensively veined with natrolite ± albite ± Cr-free jadeite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-85
locality: Přibyslavice, Kutná Hora, Bohemia, Czech Republic.
rock type: B-bearing granite.
major mineralogy: Abundant scattered oxy-schorl (type locality) with quartz and perthitic orthoclase. Minor fluorapatite and ratty muscovite (likely secondary) are also present. For the tourmaline, values of M3+/∑M (where M = Fe+Mn) between 0.078 and 0.200 normalize to oxy-schorl. For values greater than 0.200, the normalization fails altogether (i.e. the “W” site fills to greater than 1), whereas for values less than 0.078, the tourmaline normalizes to a composition not entirely consistent with either schorl or oxy-schorl. The normalization presented here uses M3+/∑M = 0.200 (the maximum mathematically permissible value).
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-85
fluorapatite (Ca4.84Mn2+0.11Sr0.01)[P3.01Si0.01O12](F0.73[OH]0.27)
oxy-schorl (maximum Fe3+) (Na0.73Ca0.02K0.010.24)(Fe2+1.52Al0.73Fe3+0.40Mg0.23Ti0.06Mn2+0.04Zn0.02)Al6.00
[Si5.72Al0.28O18](BO3)3(OH)3(O0.75F0.26)
“perthite” (orthoclase host) (K0.85Na0.09)[Si2.92Al1.05P0.03O8]
“perthite” (albite lamellae) (Na0.95K0.01)[Si2.91Al1.06P0.03O8]
muscovite (K0.83Na0.020.15)(Al1.95FeT0.06Mg0.010.98)[Si3.11Al0.89O10]([OH]1.95F0.04O0.01)

 



sample: FKM-86
locality: Långban, Filipstad, Värmland, Sweden.
rock type: Ba-Pb-As-Na-Fe metasomatite.
major mineralogy: Abundant phlogopite, with subordinate melanotekite, barite, hedyphane, an Na-(Ca)-zeolite, and calcite. A sparse aegirine-augite (containing 0.22 wt% Sc) is also present. This sample is mineralogically very similar to FKM-193, also from Långban, which also contains melanotekite and phlogopite, as well as cymrite.
(left: unpolarized light; right: under crossed polars)

 



Franklin New Jersey esperite clinohedrite and hardystonite in thin section under UV light

sample: FKM-87
locality: Franklin mining district, Sussex Co., NJ, USA.
rock type: test.
major mineralogy: esperite, hardystonite.
(upper left: unpolarized light; upper right: under crossed polars; lower: under shortwave ultraviolet [SWUV] light)

 



sample: FKM-88
locality: Franklin mining district, Sussex, Co., NJ, USA.
rock type: test.
major mineralogy: hancockite (“epidote-Pb”), andradite, clinopyroxene, barite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-89
locality: Bastnäs, Riddarhyttan, Skinnskatteberg, Västmanland, Sweden.
rock type: test.
major mineralogy: ferriallanite-(Ce), cerite-(Ce), tremolite, calcite, and an additional unknown REE-rich mineral.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-90
locality: Point of Rock quarry, Springer, Colfax Co., NM, USA.
rock type: test.
major mineralogy: specimen acquired for mangan-neptunite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-91
locality: Västanåberget, Näsum, Bromölla, Skåne, Sweden.
rock type: andalusite-muscovite schist.
major mineralogy: Scattered yellowish-green Mn-rich andalusite along with abundant muscovite. Rare clinochlore and scattered large monazite (variably Ce-dominant to La+Nd-dominant) are present.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-91
La-dominant monazite [monazite-(La)] ss (La0.28Nd0.25Ce0.23Pr0.08Ca0.06Th0.05Sm0.04Y0.03Gd0.02[HREE]0.01)[P0.91As5+0.04Si0.01O4]
Ce-dominant monazite [monazite-(Ce)] ss (Ce0.30La0.25Nd0.20Pr0.06Ca0.06Th0.05Sm0.03Y0.03Gd0.02[HREE]0.01)[P0.91As5+0.06Si0.01O4]
andalusite (Al1.81Mn3+0.15Fe3+0.03)O[Si0.98Al0.02O4]
muscovite (K0.67Na0.030.30)(Al1.90FeT0.10Mg0.08Ti0.02MnT0.010.88)[Si3.15Al0.85O10]([OH]1.95O0.05F0.01)
clinochlore (Mg4.45Al1.37MnT0.05FeT0.05Zn0.010.07)[Si2.72Al1.28O10]([OH]7.93F0.06Cl0.01O0.01)

 



sample: FKM-92
locality: Tetětice (Struhadlo?), near Klatovy, Bohemia, Czech Republic.
rock type: “skarn”? Greenschist to amphibolite facies U-V-metasomatized calcareous meta-arenite?
major mineralogy: Predominately quartz, calcite, tremolite and pyrrhotite, with minor sphalerite, uraninite, and apatite. Of notable interest is scattered goldmanite, and very sparse Cr-REE-bearing mukhinite. Mukhinite is also present in sample FKM-26, and may be more widespread in V-rich metamorphic and metasomatic rocks than typically reported.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-93
locality: Pallavaram, Chennai, Tamil Nadu, India.
rock type: test.
major mineralogy: specimen acquired for ferro-ferri-tschermakite, but no amphibole is present in this sample.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-94
locality: Broken Hill, Yancowinna Co., NSW, Australia.
rock type: test.
major mineralogy: specimen acquired for spessartine.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-95 (billet from Univ. Arizona petrology collection, courtesy of S. Baldwin, Syracuse Univ.)
locality: Isua greenstone belt, Greenland.
rock type: magnetite-amphibole-quartz gneiss. Greenschist to amphibolite facies meta-BIF (banded iron formation). At ~3.7Ga, the Isua greenstone belt is one of the oldest preserved rock sequences in the world, and is a geologically important example of Archean tectonics.
major mineralogy: Bands of quartz alternating with bands of intergrown magnetite and actinolite, with patches of calcite and scattered hydroxylapatite. A thin quartz vein roughly perpendicular to the dominant planar fabric slightly offsets the bands.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-95
magnetite Fe2+1.00(Fe3+1.99Al0.01)O4
hydroxylapatite (Ca4.97Mn2+0.01)[P3.00O12]([OH]0.54F0.38Cl0.08)
actinolite (Na0.05K0.010.94)(Ca1.84Fe2+0.10Mn2+0.06)(Mg2.54Fe2+2.40Al0.06)[Si7.87Al0.12O22]([OH]1.99Cl0.01)

 



sample: FKM-96 (billet from Univ. Arizona petrology collection, courtesy of L. Anovitz; sample ALG-85A2)
locality: Frank MacDougall Parkway roadside, Algonquin Provincial Park, Ontario, Canada.
rock type: granulite facies meta olivine ferro-gabbro.
major mineralogy: Originally olivine, cpx, (calcic?) plagioclase, ilmenite, and minor V+Cr-bearing magnetite (and possibly a bit of late-stage k-spar… it’s unclear if the minor k-spar that’s present is remnant original igneous or if it is later metasomatic accompanying the metamorphism). Due to subsequent granulite facies metamorphism (+ metasomatism?), multiple mineral corona developed between the olivine and the plagioclase, and the ilmenite and the plagioclase. Between the olivine and plagioclase, reaction rims of orthopyroxene, pargasite ± Ti-rich biotite, and garnet grew outwards from the olivine. Between the ilmenite and olivine, reaction rims of Ti-rich biotite ± pargasite grew outwards from the ilmenite. The cpx developed clouding from minute exsolution (but developed no corona), and micro-crystals of hercynite grew throughout the plagioclase. Minor apatite and Cu- and Fe-rich sulfides (several with Ni), presumably part of the primary igneous rock, seem largely unaffected by the metamorphism (although depending on the peak T, minor pyrite present may have crystallized during the cooling of the igneous rock [and was subsequently preserved during metamorphism… this would be a peak T < ~740 °C scenario], or it may have formed as a retrograde metamorphic mineral from the sulfidation of earlier igneous Fe-(Ni) sulfides… this would be a peak T > ~740 °C scenario). Likely the result of the high metamorphic grade, note that among most of the minerals, zoning is overall very muted (although the cpx fortuitously straddles a nomenclature boundary so gives the appearance of being more compositionally variable than it really is). Sparse retrograde chlorite is also present. One tiny rutile (too small to analyze well without unavoidable plagioclase overlap; however, also with >588 ppm Mn and >345 ppm Nb) was observed. The extensive accompanying analytical data were collected, normalized and interpreted entirely by a group of five undergraduate geology students as part of an analytical petrology class project (Spring 2011)… nice job, class!
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-96
pentlandite (in pyrite) (Ni4.78Fe3.99Co0.22)S8.00
chalcopyrite Cu0.98Fe1.00S2.00
pyrrhotite (Fe0.86Ni0.01)S1.00
pyrite (with pentlandite inclusion) (Fe0.92Ni0.07Co0.01)S2.00
pyrite (inclusion-free) (Fe0.98Ni0.03)S2.00
hercynite (inclusions in plagioclase) (Fe2+0.72Mg0.27)(Al1.88Fe3+0.12)O4
magnetite Fe2+1.00(Fe3+1.85V0.05Al0.04Cr0.02Ti0.02Fe2+0.02)O4
ilmenite (Fe2+0.98Mn2+0.01Fe3+0.01)(Ti0.99Fe3+0.01)O3
fluorapatite (Ca4.92Na0.05Y0.01La0.01Ce0.01Nd0.01)[P2.98Si0.02O12](F0.82[OH]0.15Cl0.03)
fayalite (Mg0.83Fe2+0.15Mn2+0.01)Fe2+1.00[Si1.00O4]
almandine (Fe2+1.70Mg0.69Ca0.53Mn2+0.08)(Al1.99Fe3+0.01)[Si2.99Al0.01O12]
“hypersthene” (Mg0.97Ca0.02Mn2+0.01)(Fe2+0.83Mg0.11Al0.05)[Si1.97Al0.03O6]
diopside-rich cpx ss (Ca0.85Mg0.08Na0.07Mn2+0.01)(Mg0.59Fe2+0.31Al0.07Fe3+0.02Ti0.01)[Si1.96Al0.04O6]
augite-rich cpx ss (Ca0.81Mg0.11Na0.08Mn2+0.01)(Mg0.56Fe2+0.32Al0.07Fe3+0.04Ti0.01)[Si1.95Al0.05O6]
magnesio-hastingsite
(adjacent to magnetite)
(Na0.58K0.250.17)(Ca1.75Na0.25)(Mg2.06Fe2+1.23Fe3+0.80Al0.51Ti0.36V0.01Mn2+0.01)
[Si6.08Al1.91O22]([OH]1.23O0.71F0.05Cl0.01)
magnesio-hastingsite
(adjacent to opx)
(Na0.50K0.320.18)(Ca1.78Na0.22)(Mg2.22Fe2+1.10Fe3+0.80Al0.47Ti0.38V0.01Mn2+0.01)
[Si6.09Al1.90O22]([OH]1.20O0.75F0.03Cl0.01)
magnesio-hastingsite
(adjacent to garnet)
(Na0.48K0.320.20)(Ca1.79Na0.21)(Mg2.22Fe2+1.12Fe3+0.77Al0.48Ti0.38V0.02Mn2+0.01)
[Si6.13Al1.87O22]([OH]1.20O0.75F0.04Cl0.01)
phlogopite (K0.93Ba0.03Na0.020.02)(Mg1.18FeT1.23Ti0.45Al0.040.10)[Si2.77Al1.23O10]([OH]1.07O0.90F0.03Cl0.01)
clinochlore (Ca0.02K0.01Na0.01)(Mg2.71FeT1.98Al0.69MnT0.020.60)[Si3.45Al0.55O10]([OH]7.99F0.01)
orthoclase (K0.95Na0.03)[Si2.97Al1.02O8]
“oligoclase” plag ss (most Ca-rich) (Na0.72Ca0.28K0.03)[Si2.70Al1.30O8]
“oligoclase” plag ss (most Na-rich) (Na0.77Ca0.20K0.04)[Si2.79Al1.21O8]

 



sample: FKM-97 (billet from Univ. Arizona petrology collection, Krentz collection, sample K-249)
locality: Bohemia, Czech Republic.
rock type: hedenbergite-garnet “eclogite”. This rock is purported to be an eclogite (and indeed it may be), but it is compositionally very different from a typical metabasite-protolith eclogite (for example, see sample FKM-34). In some respects the rock resembles a skarn-like calc-silicate, but even if this rock was originally of metasomatic origin, it still appears to have undergone subsequent high grade metamorphism (to mute any pre-existing zoning). One could imagine this rock is perhaps an eclogite facies metasomatic garnetite.
major mineralogy: This rock is very dense, notably deeply-colored, and nearly all garnet (straddling the grossular-andradite composition boundary, with a significant almandine component), with less abundant slightly-Na-enriched hedenbergite (but not Na-rich enough to be considered the omphacite/aegirine-augite of classic mafic eclogite). Scattered apatite and epidote are also present. The cpx is unzoned; the garnet is at best weakly patchy zoned, although small garnet crystals completely enclosed in cpx do differ somewhat in composition from the more abundant, larger, external (to cpx) garnet masses.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-97
fluorapatite (Ca4.98Sr0.01)[P2.99Si0.01O12](F0.65[OH]0.34)
grossular
(isolated inclusions in cpx)
(Ca2.95Fe2+0.03Mn2+0.02)(Al1.39Fe3+0.51Ti0.08Mg0.01Fe2+0.01)[Si2.92Al0.060.01O11.94F0.06]
grossular-rich garnet ss
(bulk)
(Ca2.59Fe2+0.38Mn2+0.02Mg0.01)(Al1.05Fe3+0.91Ti0.02Mg0.01)[Si2.99Al0.01O11.99F0.01]
andradite-rich garnet ss
(patchy in bulk grossular)
(Ca2.67Fe2+0.30Mn2+0.02Mg0.01)(Fe3+1.21Al0.76Ti0.02)[Si2.97Al0.02O11.99F0.01]
epidote Ca1.00(Ca0.96Sr0.02)Al1.02Al1.00(Fe3+0.74Al0.25Ti0.01)O[Si0.99Al0.01O4][Si1.98Al0.02O7](OH)
hedenbergite (Ca0.93Na0.07)(Fe2+0.46Mg0.43Fe3+0.11Al0.01)[Si1.95Al0.05O6]

 



sample: FKM-98
locality: Kola Peninsula, Murmanskaja Oblast’, Russia.
rock type: intrusive eudialyte-pyroxene pegmatite (lujavrite?)
major mineralogy: test.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-99 (billet from Univ. Arizona petrology collection, courtesy of S. Baldwin; sample NC-55)
locality: Mayavetch River, Pouébo terrane, northern New Caledonia.
rock type: garnet-glaucophane schist. Blueschist facies retrogressed eclogite facies metabasite. Compare this sample to the more phengite-rich FKM-100, also from the Mayavetch River area.
major mineralogy: test.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-100 (billet from Univ. Arizona petrology collection, courtesy of S. Baldwin; sample NC-57)
locality: Mayavetch River, Pouébo terrane, northern New Caledonia. Compare this sample to the less phengite-rich FKM-99, also from the Mayavetch River area.
rock type: garnet-phengite-glaucophane schist. Blueschist facies.
major mineralogy: test.
(left: unpolarized light; right: under crossed polars)

 



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