Elsevier

Sedimentary Geology

Volume 93, Issues 1–2, October 1994, Pages 85-105
Sedimentary Geology

Changes in garnet chemistry show a progressive denudation of the source areas for Permian-Jurassic sandstones, Southern Kitakami Terrane, Japan

https://doi.org/10.1016/0037-0738(94)90030-2Get rights and content

Abstract

Garnet is a widespread detrital mineral in Permian-Jurassic sandstones of the Southern Kitakami Terrane. Electron-probe microanalyses of these garnets show a gradual change of chemistry with the age of the sandstones. The dominant garnet suites in Permian-Triassic sandstones are grandite, with some spessartine-almandine in Upper Triassic sandstones. However, in Lower Jurassic sandstones, pyrope-almandine and spessartine-almandine garnets are common, whereas grandite garnets are absent. Garnet suites in Middle to Upper Jurassic sandstones are dominated by pyrope-almandine garnet. The grandite-dominant suites are associated with hornblende, epidote and titanite, whereas the pyrope-almandine-dominant suites are associated with biotite.

These grandite garnets are rich in andradite and have very low spessartine, almandine and pyrope contents. Some of the grandite garnets are anisotropic with oscillatory zoning and sector twinning, typical of calcic skarn deposits. Spessartine-almandine garnets are common in low-grade metamorphic rocks. The diverse suites of pyrope-almandine garnets (up to 42 mol.% pyrope) from the Jurassic sandstones are typical of epidote-amphibolite to granulite facies metamorphic rocks.

The chemistry and optical properties of garnets and the heavy-mineral data show that low-grade or contact metamorphic rocks such as skarns and hornfelses were widely exposed in the source areas of the Permian-Triassic sandstones. High-grade metamorphic rocks, including granulites and intrusive rocks, appeared in Early Jurassic time and were widespread during the Middle Jurassic. The critical change in the source areas for the Southern Kitakami Terrane occurred during Late Triassic to Early Jurassic time, and may correspond to the Indosinian movements associated with the collision between the North China and South China blocks.

References (52)

  • M.T. Einaudi et al.

    Introduction—terminology, classification, and composition of skarn deposits

    Econ. Geol.

    (1982)
  • M.T. Einaudi et al.

    Skarn deposits

    Econ. Geol., 75th Anniversary Volume

    (1981)
  • K. Ichikawa

    Note on the basal conglomerate of Triassic Inai Group in the Okatzu District, Miyagi Pref., NE Japan

    Mineral. Geol.

    (1951)
  • B. Jamtveit et al.

    Zonation patterns of skarn garnets: records of hydrothermal system evolution

    Geology

    (1993)
  • K. Kamada

    Geology of the Tsuya district

  • S. Kanisawa et al.

    K-Ar ages of amphibolites from the Matsugadaira-Motai Metamorphics and their significance

    J. Min. Petrol. Econ. Geol.

    (1992)
  • H. Kano

    On a basal conglomerate of the Inai Formation (Lower Triassic) in the Toyoma district, Southern Kitakami-mountainland, Japan — Studies on the granite-bearing conglomerates in Japan, 2

    J. Geol. Soc. Jpn.

    (1958)
  • H. Kano

    On the pebble of metamorphic rocks found in the Usuginu-type conglomerates and their geologic significance — Studies on the granite-bearing conglomerates in Japan, 6

    J. Geol. Soc. Jpn.

    (1959)
  • H. Kano

    On the granite-pebbles from the Shishiori Formation (Upper Jurassic) and their origin — Studies on the granite-bearing conglomerates in Japan. 7

    J. Geol. Soc. Jpn.

    (1959)
  • H. Kano

    Studies on the Usuginu conglomerates in the Kitakami Mountains — Studies on the granite-bearing conglomerates in Japan, 22

    J. Geol. Soc. Jpn.

    (1971)
  • M. Kawamura

    On the geology of the Hayachine Tectonic Belt

    Chikyu Kagaku (Earth Science)

    (1988)
  • M.P. Klimetz

    Speculations on the Mesozoic plate tectonic evolution of eastern China

    Tectonics

    (1983)
  • R. Kretz

    Symbols for rock-forming minerals

    Am. Mineral.

    (1983)
  • B.E. Leake

    Nomenclature of amphiboles

    Am. Mineral.

    (1978)
  • H. Maekawa

    Geology of the Motai Group in the southwestern part of the Kitakami Mountains

    J. Geol. Soc. Jpn.

    (1981)
  • K. Minoura

    Where did the Kitakami and Abukuma come from? — tectonic history of the Northeast Japan

    Kagaku

    (1985)

    • Cited by (0)

    View full text
    Copyright © 1994 Published by Elsevier B.V.