Petrochemical Stratigraphy of Cumulate Enclave Bearing Andesites from Karapınar-Karacadag Volcanic Complex (Konya, Central Anatolia)

Abstract

Amphibole and pyroxene major and trace element compositions from the cumulate enclave bearing andesites from the Karapınar - Karacadag Volcanic Complex, in Konya (Turkey), have been analyzed by electron microprobe and laser ablation inductively coupled plasma mass spectrometry. A petrochemical stratigraphy can be interpreted for the rocks by using major and trace element contents of the minerals and their changes from center to rim. Amphibole (GK-35C1) of the cumulate enclave, from core to rim, contains Li = 107-103-112 ppm, Ti = 7760-6120-772 ppm, V = 410-342-415 ppm, Cr = 149-166-249 ppm, Zr = 79-94-88 ppm, Mn = 1764-1961-1726 ppm. However host rock’s amphibole grain (GK-35C6), from core to rim, includes Li = 52-111-97 ppm, Ti = 7760-6120-772 ppm, V = 496-520-351 ppm, Cr = 10-69-11 ppm, Zr = 117-53-50 ppm, Mn = 1790-2723-3300 ppm. Moreover, pyroxene from the host rock has 10.7-8.5-11.6 ppm Li, 1230-658-1933 ppm Ti, 162-114- 202 ppm V, 29-7-1420 ppm Cr, 31-16-42 ppm Zr, 4010-3721-2422 ppm Mn. Amphibole thermobarometer calculations have yielded temperature and pressure estimates 993-915°C and 5-2.17 kbar for enclave and host rock, respectively. Also, clinopyroxene geothermobarometer calculations have given 1.34 kbar pressure and 1116°C temperature. Especially the mineral chemistry data of amphiboles and pyroxenes show that the cumulate enclave is more primitive than its host, and enclave were formed at an earlier stage. Geothermobarometer calculations also indicate that the amphiboles in the enclave was formed at a deeper depth than the pyroxenes in the host and the enclave was broken off during convection in the magma chamber and brought to the host. Oscillatory and reverse zonning in terms of Li, Ti, Zr, Hf, Cr, V contents in the minerals indicate magma replenishment. In the host rock, decreasing in Zr and Hf contents from core to rim shows co-magmatic zircons with the amphiboles. Ti negative anomaly in the amphiboles exhibits that they crystallized after Fe-Ti oxide formation. In the light of the mineral chemistry data, Petrochemical stratigraphy (P) should be as in the bottom. P1) Formation of the amphibole cores in the cumulate enclave, after Fe-Ti oxides formations P2) Recharging of the amphiboles in the enclave, P3) Formation of the host rock’s amphibole cores and crystallization of comagmatic zircons P4) Breaking off the cumulate enclaves with convection and settling in the host rock, while the recharging of the host rock amphiboles, P5) Formation of host rock’s pyroxene cores, P6) recharging of the pyroxenes P7) crystallization of the plagioclase and quartz minerals in the shallow depths of the upper crust.