Whole-rock chemical compositions and K-Ar ages of the Tadamigawa granitic rocks, southwestern part of Fukushima Prefecture, northeastern Japan

The rock from Skye which Harker called marscoite was recognized by him to be hybrid in origin because of the close association in the rock of basic plagioclase, quartz and orthoclase. The position of marscoite in the sequence of rocks forming the Western Red Hills Tertiary complex has now been defined, and evidence for its parentage and the mechanics of its formation obtained. The Western Red Hills intrusive centre, developed after the Cuillin and before the Broadford centres, as suggested by J. E. Richey, consists of five different, high-level granitic intrusions which were followed by a southern and northern series of late intrusions, including marscoites, ferrodiorites, and various additional granitic rocks. The high-level granitic rocks of Skye, which have so far been loosely termed granophyres, cannot all properly be described as such, and the term epigranite is proposed as a general name for them. The earliest rocks belonging to the southern late intrusions are porphyritic epigranites and felsites, having quartz and potash felspar phenocrysts resembling the xenocrysts of these minerals in the marscoite. Then came marscoite, somewhat chilled against the felsite but also back-veined by it. The marscoite in Harker’s Gully, and in other places on Marsco, passes gradually into ferrodiorite which sometimes contains basic andesine phenocrysts similar to the xenocrysts of the marscoite. The ferrodiorite has a composition suggesting that it was derived by extreme fractional crystallization of basic magma. The xenocrysts of the marscoite are highly characteristic and indicate that marscoite was formed by the mixing of a porphyritic acid magma, like that which produced the Southern Porphyritic Felsite, and a porphyritic basic magma, like that which produced the porphyritic ferrodiorite of Marsco. The chemical compositions of the presumed parent materials and marscoite support this view. Because of the even distribution of the xenocrysts in marscoite, the mixing must have been largely effected by the mechanical stirring together of two liquids, in both of which were suspended crystals. Diffusion within the liquid phase must also have contributed in some degree to the ultimate homogeneity of the liquid part of the mixture. The origin of the marscoite of the northern late intrusions is presumably similar to that of the southern, except that the basic parent is believed to be represented by the porphyritic hawaiite blocks in the northern marscoite. The northern marscoite cuts through, and is chilled against, the Glamaig, Eas Mor, and Maol na Gainmhich epigranites. Inwards from the contacts, the marscoite gives place, in a distance of 30 to 50 yd., to a rock here called glamaigite, which consists of rounded, dark patches, usually an inch or so across, and a less dark matrix, in approximately equal amounts. In both dark and light material there are xenocrysts of andesine, potash felspar and quartz, as in the marscoite. The difference in composition of the darker and lighter parts of the rock is not great, but is such as to suggest that the darker would have had a slightly higher temperature range of crystallization. The glamaigite is believed to have originated from a less well-homogenized mixture of basic and acid porphyritic magmas. From the mixture, the slightly more basic parts solidified first, and then flow movements of the magma resulted in rounding of the early semi-solid clots of hybrid material. The central parts of the composite, northern, late intrusions consist of a rock resembling glamaigite but tending to be more uniform and acid in composition. The greater homogeneity of this rock, distinguished as dioritic glamaigite, may be due to its central position within the intrusions, where slower cooling would allow more time for diffusion. It is suggested that the epigranites of the Hebridean igneous province originated by melting of crustal rocks of broadly granitic composition. The heat to produce the melting is believed to have been derived from basic magma intruded into the earth’s crust, the upward transfer of heat being aided by convection in the magma and bottom accumulation of early formed crystals. At some stage, a residual layer of ferrodiorite or hawaiite liquid, produced by fractionation, may have underlain a granitic liquid produced by melting. Two separate systems of convection currents are envisaged in the two liquids, because of the differing densities. At the junction of the two systems of currents, where they would be flowing in opposite directions, there would be an opportunity for mechanical mixing. Ultimately, a mass of hybrid magma may have developed, annular in form and with a forced circulation, which was the source of the marscoite and related rocks.

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The petrochemistry of some Lewisian granitic rocks

Mineralogical Magazine and Journal of the Mineralogical Society ◽

10.1180/minmag.1967.036.279.06 ◽

1967 ◽

Vol 36 (279) ◽

pp. 342-363 ◽

Cited By ~ 7

Author(s):

D. R. Bowes

Keyword(s):

Experimental Data ◽

Granitic Rocks ◽

Chemical Compositions ◽

North West ◽

Mineral Solubility ◽

The North

SummaryThe chemical compositions of eighty granitic rocks from the Lewisian of the North-West Highlands of Scotland, particularly from the Gairloch district, are set out in relation to geological occurrence and their normative proportions of albite, orthoclase, quartz, and anorthite compared with experimental data relating to the systems NaAlSi3O8-KAlSi3O8-SiO2-H2O and KAlSi3O8-NaAlSi2O8-CaAl2Si2O8-SiO2. The field of composition for these Lewisian rocks moves from Ab-Q-rich for autochthonous granites to Ab = Or = Q (approximately) for parautochthonous granites to Or-rich for intrusive granites. This trend is related to the varying roles of mineral solubility under stress, selective melting, and potassium metasomatism.

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Shear Wave Splitting Observed in the Southwestern Part of Fukushima Prefecture, Notheastern Japan.

Journal of Physics of the Earth ◽

10.4294/jpe1952.42.303 ◽

1994 ◽

Vol 42 (4) ◽

pp. 303-319 ◽

Cited By ~ 10

Author(s):

Tomomi Okada ◽

Akira Hasegawa ◽

Toru Matsuzawa ◽

Satoshi Matsumoto ◽

Koichi Nida ◽

...

Keyword(s):

Shear Wave ◽

Shear Wave Splitting ◽

Southwestern Part ◽

Fukushima Prefecture ◽

Wave Splitting

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The chemistry of allanite from the Daibosatsu Pass, Yamanashi, Japan

Mineralogical Magazine ◽

10.1180/0026461056940259 ◽

2005 ◽

Vol 69 (4) ◽

pp. 403-423 ◽

Cited By ~ 16

Author(s):

M. Hoshino ◽

M. Kimata ◽

N. Nishida ◽

A. Kyono ◽

M. Shimizu ◽

...

Keyword(s):

Crystal Structure ◽

Hydrogen Bond ◽

Major Elements ◽

Granitic Rocks ◽

Homogeneous Distribution ◽

Chemical Compositions ◽

Island Arcs ◽

Scattered Electron ◽

The Difference ◽

Difference Fourier

AbstractThe crystal structure of allanite from granitic pegmatite, the Daibosatsu Pass, Yamanashi, Japan, has been refined under the constraint of chemical composition determined by electron microprobe analysis of rare earth elements. Back-scattered-electron images and X-ray element maps of the allanites show that each of their crystal grains has chemically homogeneous distribution of major elements. A typical formula for the chemistry is: (Ca0.920☐0.080)Σ1.000(La0.238Ce0.443Pr0.048Nd0.100Sm0.019Th0.042Mn0.008☐0.102)Σ1.000(Al0.607Fe0.3173+Ti0.076)Σ1.000(Al1.000)(Fe0.5432+Fe0.3653+Mn0.055Mg0.037)Σ1.000(SiO4)(Si2O7)O(OH).The crystal structure of allanite, monoclinic, a 8.905 (1), b 5.7606 (5), c 10.123 (1) Å, β 114.78°(1), space group P21/m, Z = 2, has been refined to an unweighted R factor of 3.46% for 1459 observed reflections. Although the H atom position was not determined on the Difference-Fourier map, inspection of the bond valence sums demonstrates that the H atom is uniquely located at the O10 atom and involved in a hydrogen bond to O4. A systematic examination as to crystal chemistry of allanites suggests that the isolated SiO4 tetrahedron has the largest distortion of three kinds of the tetrahedron containing Si2O7 groups in the allanite structure. This observation is common to the epidote group minerals, while the larger distortion of A2 sites caused by occupancy by REE in allanites contrasts with the smaller one of A sites in other epidote group minerals. In the allanite groups the bond angles between the O10–H bond and hydrogen bond H···O4 are found to range from 170 to 180°.Compilation of the chemical compositions of the title allanite and the others from granitic rocks, Japan, which reveals Th-incorporation as the coupled substitution of 3Th4+ + ☐ (vacancy) ⇌ 4REE3+, provides an explanation for the observation that higher Th concentrations characterize allanites from the island arcs. The ternary Al2O3-Fe2O3-ΣREE diagram illustrates that allanites are grouped, according to their origins, into three classes suggestive of tectonic backgrounds for the crystallization localities; (1) intracontinental, (2) island arc and (3) continental margin.

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Mineralogy of Phoscorites of the Arbarastakh Complex (Republic of Sakha, Yakutia, Russia)

Minerals ◽

10.3390/min11060556 ◽

2021 ◽

Vol 11 (6) ◽

pp. 556

Author(s):

Mikhail Nikolaevich Kruk ◽

Anna Gennadievna Doroshkevich ◽

Ilya Romanovich Prokopyev ◽

Ivan Aleksandrovich Izbrodin

Keyword(s):

Mineral Composition ◽

Siberian Craton ◽

Chemical Compositions ◽

Textural Features ◽

Carbonatite Complex ◽

Southwestern Part ◽

Modal Composition ◽

Accessory Minerals ◽

Ree Mineralization ◽

Primary Minerals

The Arbarastakh ultramafic carbonatite complex is located in the southwestern part of the Siberian Craton and contains ore-bearing carbonatites and phoscorites with Zr-Nb-REE mineralization. Based on the modal composition, textural features, and chemical compositions of minerals, the phoscorites from Arbarastakh can be subdivided into two groups: FOS 1 and FOS 2. FOS 1 contains the primary minerals olivine, magnetite with isomorphic Ti impurities, phlogopite replaced by tetraferriphlogopite along the rims, and apatite poorly enriched in REE. Baddeleyite predominates among the accessory minerals in FOS 1. Zirconolite enriched with REE and Nb and pyrochlore are found in smaller quantities. FOS 2 has a similar mineral composition but contains much less olivine, magnetite is enriched in Mg, and the phlogopite is enriched in Ba and Al. Of the accessory minerals, pyrochlore predominates and is enriched in Ta, Th, and U; baddeleyite is subordinate and enriched in Nb. Chemical and textural differences suggest that the phoscorites were formed by the sequential introduction of different portions of the melt. The melt that formed the FOS 1 was enriched in Zr and REE relative to the FOS 2 melt; the melt that formed the FOS 2 was enriched in Al, Ba, Nb, Ta, Th, U, and, to a lesser extent, Sr.

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Tracking and Evaluating the Concentrations of Natural Radioactivity According to Chemical Composition in the Precambrian and Mesozoic Granitic Rocks in the Jangsu-gun Area, Central Southwestern South Korea

Minerals ◽

10.3390/min11070684 ◽

2021 ◽

Vol 11 (7) ◽

pp. 684

Author(s):

Sung Won Kim ◽

Weon-Seo Kee ◽

Saro Lee ◽

Byung Choon Lee ◽

Uk Hwan Byun

Keyword(s):

South Korea ◽

Natural Radioactivity ◽

Indoor Radon ◽

Early Jurassic ◽

Granitic Rocks ◽

Late Triassic ◽

Accessory Mineral ◽

Chemical Compositions ◽

Activity Concentrations ◽

The Mean

The Jangsu-gun area in the central Southwestern South Korea consists of a well-preserved Middle Paleoproterozoic gneissic basement, as well as the Late Triassic and Early Jurassic granitic rocks. Here, we present the detailed zircon U-Pb age data and whole-rock chemical compositions, including radioactive elements (e.g., U and Th) and activity concentrations of 226Ra, 232Th and 40K for the Middle Paleoproterozoic gneisses, and Late Triassic and Early Jurassic granitic rocks of the Jangsu-gun area. The Middle Paleoproterozoic gneissic basement, and the Late Triassic and Early Jurassic granitic rocks have ages of ca. 1988 Ma and 1824 Ma, 230 Ma and 187–189 Ma, respectively. Geochemically, the Middle Paleoproterozoic orthogneiss, Late Triassic granites and Early Jurassic granitic rocks show typical arc-related metaluminous to weakly peraluminous fractionated granite features with ASI (aluminum saturation index) values of 0.92 to 1.40. The mean values of U (ppm) and Th (ppm) of the Middle Paleoproterozoic orthogneisses (6.4 and 20.5, respectively), Late Triassic granites (1.5 and 10.9), and Early Jurassic granites (3.5 and 16.5) were similar to those (5 and 15) of the granitic rocks in the Earth’s crust. The mean 226Ra (Bq/kg), 232Th (Bq/kg), and 40K (Bq/kg) activity concentrations and radioactivity concentration index (RCI) are 62, 71, 1,214 and 0.96 for the Middle Paleoproterozoic orthogneisses; 16, 39, 1,614 and 0.78 for the Late Triassic granites; and 56, 70, 1031 and 0.88 for the Early Jurassic granitic rocks, respectively. The U, Th, 226Ra, 232Th, 40K, and RCI of the Middle Paleoproterozoic biotite paragneisses are similar to those of the Middle Paleoproterozoic orthogneisses. The trend of 226Ra, 232Th, and 40K activity concentrations, and the composition of U and Th from the Precambrian and Mesozoic rocks in the Jangsu-gun area indicates that monazite is the main accessory mineral controlling the concentration of natural radioactivity. Based on a detailed examination of the natural radioactivity in the rocks of the Jangsu-gun area, the Middle Paleoproterozoic orthogneisses and paragneisses, and Late Triassic and Early Jurassic granitic rocks show average high mean RCI values of 0.88−0.96, such that 32% of the rocks exceeded the recommended value of one in the guidelines for the RCI in South Korea. Especially, the RCI is closely related to the radon levels in the rocks. As a result, the Jangsu-gun area in South Korea is a relatively high radiological risk area, which exhibits higher indoor radon levels in the residences, compared with residences in the other areas in South Korea.

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