The anatomy of a gabbro body and its bearings on the origin of mafic enclaves in the Ağaçören granitoid central Turkey

1996-01-01
Güleç, Nilgün Türkan
Toprak, Vedat
Yusuf Kagan, Kadıoglu
Barbara, Barreıro
The origin of mafic enclaves and mafic magmatic rocks associated with the Cretaceous Aǧaçören granitoid (central Turkey) was investigated through field, petrographic, and geochemical studies along a contact between enclave-bearing granite and a gabbro body exposed at the top of the granite. Three zones were distinguished within the gabbro, from center to margin: massive gabbro, transitional gabbro, and shattered gabbro. Petrographic features display a continuous change from massive to shattered gabbro, represented by an increase in the biotite/hornblende ratio and in the amount of interstitial quartz, and a decrease in color index. These changes are accompanied by the appearance, towards shattered gabbro, of specific textural features (acicular apatite and blade-shaped mafic minerals) which record the evidences of magma mixing. Geochemically, gabbro and granite have enrichment in Large Ion Lithophile (LIL), with respect to High Field Strength (HFS) elements, suggesting derivation from a subduction-modified upper mantle and/or a mixture of mantle and crustal components. Element enrichment levels increase from massive gabbro towards granite and are accompanied by an increase in 87Sr/86Sr, and a decrease in 143Nd/144Nd ratios. Enclaves have petrographic features similar to those of shattered gabbro, and geochemical features intermediate between granite and gabbro. Overall, the gabbro-enclave-granite spectrum appears to record the interaction between mafic and felsic magmas in a silicic magma chamber replenished by mafic influx from an isotopically enriched mantle. Constraints from isotope data point to an increase in the relative proportion of the mafic magma from 30% in granite to 90% in gabbro.
Citation Formats
N. T. Güleç, V. Toprak, K. Yusuf Kagan, and B. Barbara, “The anatomy of a gabbro body and its bearings on the origin of mafic enclaves in the Ağaçören granitoid central Turkey,” pp. 169–192, 1996, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/84276.