RELATIVE INVOLVEMENT OF MANTLE AND CRUSTAL COMPONENTS IN THE AGACORENGRANITOID (CENTRAL ANATOLIA, TURKEY) - ESTIMATES FROM TRACE-ELEMENT AND SR-ISOTOPE DATA
N. Gulec et Yk. Kadioglu, RELATIVE INVOLVEMENT OF MANTLE AND CRUSTAL COMPONENTS IN THE AGACORENGRANITOID (CENTRAL ANATOLIA, TURKEY) - ESTIMATES FROM TRACE-ELEMENT AND SR-ISOTOPE DATA, Chemie der Erde, 58(1-2), 1998, pp. 23-37
Trace element contents, together with Sr-isotope ratios on a limited n
umber of samples, are reported for the central part of the Agacoren gr
anitoid in central Anatolia (Turkey), Trace element contents are depic
ted in terms of Ocean Ridge Granitoid (ORG)-normalized elemental patte
rns. The patterns display similarities to Volcanic Arc Granitoids (VAG
) and/or Collision Granitoids (COLG), and are characterized by enrichm
ent in Large Ion Lithophile (LIL) elements relative to High Field Stre
ngth (HFS) elements, negative Ba and positive Rb, Th and Ce anomalies,
and high Th/Nb ratios. A comparison with the patterns typical of uppe
r continental crust, lower continental crust and volcanic are calc-alk
aline basalt implies that the Agacoren granitoid inherited its pattern
essentially from the upper crust, although inheritance-in part-from a
subduction modified upper mantle is also possible. Plot of Rb/Sr rati
os against the initial Sr-87/Sr-86 ratios at the time of granitoid int
rusion (110 Ma) suggests the derivation of granitoid from a mixture of
about 70% (upper) crustal + 30% mantle components, the mixture later
undergoing a maximum of about 21% fractional crystallization. The rela
tive proportion of mantle and crustal components, as constrained from
the isotope data, exceeds the limits-for complete hybridization-impose
d by mechanical and thermal arguments, but falls into the range for co
mmingling (incomplete mixing) of mafic and felsic magmas, the validity
of which is also supported by the presence of mafic microgranular enc
laves in the granitoid. The modeling of trace element data based on th
e estimates from isotope data yield elemental patterns generally confo
rmable to those displayed by granitic samples.