Low-temperature recrystallization of Franciscan greywackes from Pacheco Pass, California.

S. Maruyama, J. G. Liou, Y. Sasakura

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Low-T metamorphism of the Franciscan complex at Pacheco Pass occurred at P-T conditions near the so-called jadeite isograd. In a W-E traverse, four distinct prograde metamorphic zones are defined: 1) albite-quartz zone, 2) albite-rich, albite-quartz-clinopyroxene assemblage, 3) clinopyroxene-rich, albite-quartz-clinopyroxene assemblage and 4) clinopyroxene zone. Metamorphic pyroxenes are restricted to zones I-IV in metagreywackes, but metabasites contain augite-rich pyroxenes even in zone I. With increasing grade, the compositions of pyroxenes in metagreywackes change from virtually Jd100 in zone II to approx Jd60 in zone III. The metamorphic T is estimated to have been approx 170oC in zones I and II and approx 230oC in zones II and III; P estimates range 4.5-8 kbar. A gently folded thermal structure for the Cretaceous subduction metamorphism is postulated for this area.-R.A.H.

Original languageEnglish
Pages (from-to)345-355
Number of pages11
JournalMineralogical Magazine
Volume49
Issue number3
Publication statusPublished - 1985
Externally publishedYes

Fingerprint

Quartz
albite
clinopyroxene
Temperature
quartz
metamorphism
Chemical analysis
jadeite
metabasite
augite
P-T conditions
thermal structure
subduction
Cretaceous

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Low-temperature recrystallization of Franciscan greywackes from Pacheco Pass, California. / Maruyama, S.; Liou, J. G.; Sasakura, Y.

In: Mineralogical Magazine, Vol. 49, No. 3, 1985, p. 345-355.

Research output: Contribution to journalArticle

Maruyama, S, Liou, JG & Sasakura, Y 1985, 'Low-temperature recrystallization of Franciscan greywackes from Pacheco Pass, California.', Mineralogical Magazine, vol. 49, no. 3, pp. 345-355.
Maruyama, S. ; Liou, J. G. ; Sasakura, Y. / Low-temperature recrystallization of Franciscan greywackes from Pacheco Pass, California. In: Mineralogical Magazine. 1985 ; Vol. 49, No. 3. pp. 345-355.
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