| Autor: |
Sharov, V., Sizykh, Yu., Fefelov, N. |
| Zdroj: |
Lithology & Mineral Resources; Jan2002, Vol. 37 Issue 1, p82-91, 10p |
| Abstrakt: |
Metapelites as products of isochemical regional metamorphism retain a memory on paleoclimate and geochemical evolution of clays. At the base of metasedimentary sequences, they are composed of high-Al varieties containing modal and normative pyrophyllite locally in association with chloritoid. The clayey rocks are relatively Al-depleted in middle part of the section but Al-rich and pyrophyllite-free at the top. The lower high-Al metasedimentary rocks could have been derived from mature kaolinite and kaolinite-bearing hydromuscovite–chlorite clays. The middle low-Al metapelites are considered to be relatively immature montmorillonite-bearing illite clays, and the upper high-Al varieties are interpreted as relatively mature illite–chlorite clays without kaolinite. The evolution of clays imprinted in geochemical signatures of metamorphic rocks was predetermined by the cooling of moderately humid climate in middle periods of sedimentary cycles related to the development of alpine glacial topography on the northern Patom Highland. Periodic variations of chemical and mineral compositions of rocks were used as helpful guides for the determination of boundaries and volumes of primary sedimentary cycles in metasedimentary sequences with obliterated stratigraphy. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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