AGE OF THE MURMANO PLUTON AND ITS RELATIONSHIP WITH THE OPHIOLITES

Year 1988, Volume: 108 Issue: 108, 34 - 34, 01.01.1988

H.p. Zeck Taner Ünlü

Abstract

The composite Murmano pluton (a few km NNW of the town of Divriği, province of Sivas, Eastern Central
Anatolia), ranging from quartz-syenitic to dioritic in composition, is intrusive into serpentinhes belonging to the Divriği ophiolite
complex. The pluton gives a 110±5 Ma (IV) Rb-Sr whole rock isochron date which is interpreted to represent the age of the
intrusion. A series of 7 samples, one micro quartz syenite, 5 monzonites and one hydrothermal scapolite rich dyke rock, together
representing a c. 100 by 200 m large area at the southern margin of the pluton, defines a 112 +8 Ma(lV) Rb-Sr whole rock isochron
with an initial
87
Sr/86
Sr ratio of 0.7068. Another series of 7 samples representing ac.200 by 500 m large area at the southwestern
margin of the pluton gives a 5 point 109±5 Ma (IV) isochron with an initial
87Sr/86
Sr ratio of 0.7058. The two concordant dates
are interpreted as the age of intrusion which is thus given as 110±5 Ma (IV). The two sample series represent two separate magma
batches which may have originated by anatexis of different source rock complexes with different Rb-Sr isotopic ratios. The
predominantly silicic character of the pluton combined with its considerable size c.25 km excludes an origin in the oceanic
realm. The magma was intruded subsequent to the obduction of the ophiolite complex which is thus suggested to have taken
place more than 110±5 Ma ago.

Keywords

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