Yurdal Genç

Late Cretaceous coeval acidic and basic magmatism, Karacaali Magmatic Complex, Central Anatolia, Turkey

The Central Anatolia Crystalline Complex (CACC) is characterized by Late Cretaceous high-temperature metamorphic rocks intruded by S-, I-, and A-type granitoids. Coeval basic plutonic and volcanic rocks also crop out in the complex. The NE–SW-trending Karacaali Magmatic Complex (KMC) represents a clear example of synchronous basic and acidic magmatic associations. We present new data on this coeval magmatism. The KMC plutonic rocks mainly consist of monzonite, granite, and gabbro, whereas the associated volcanic rocks are chiefly of basalt and rhyolite. All of the units have been cut by quartz, quartz-tourmaline, and calcite veins and by porphyritic leucogranite, aplitic, and basaltic dikes. The rhyolitic, basaltic, and gabbroic samples yield well-defined 40Ar/39Ar plateau ages of 69.1 ± 1.3, 58 ± 10, and 66.4 ± 1 million years, respectively; these data indicate that a younger multiphase basic magma was injected into a partially crystallized monzonitic magma chamber. The basic intrusions added heat to the system and gave rise to the re-fusion of the already crystallized parts of the monzonitic melt, forming the younger leucogranitic magma. The gradational contacts, cross-cutting relationships, trace element contents, trace element patterns, rare-earth element (REE) patterns, and 40Ar/39Ar geochronological data of the studied igneous suite clearly demonstrate that the acidic and basic rocks of the KMC were contemporaneous and are produced by partial melting of distinct sources rather than by fractional crystallization of a single source.

Magma mixing and unmixing related mineralization in the Karacaali Magmatic Complex, central Anatolia, Turkey

Abstract The calc-alkaline Karacaali Magmatic Complex (KMC), in the Central Anatolian Crystalline Complex, is an example of an Upper Cretaceous post-collisional I-type, plutonic–volcanic association. Volcanic rocks grade from basalt to rhyolite, whilst coeval plutonic rocks range from gabbro to leucogranite. In this paper we document evidence for the occurrence of both mixing and unmixing during the evolution of this igneous complex. Mixing of mafic and felsic magmas was observed in petrographic properties at microscopic to macroscopic scales and is further supported by mineral chemistry data. The occurrence of unmixing is evidenced in the Fe and Cu–Mo mineralization hosted in the KMC. The iron mineralization in basaltic-andesitic rocks consists mostly of magnetite. Magnetite has been grouped into four settings: (1) matrix type; (2) vein-filling type; (3) breccia matrix type; and (4) vesicle-filling type. In contrast, Cu–Mo mineralization is related to vertical north–south trending quartz-, quartz-calcite-, and quartz-tourmaline veins crosscutting monzonitic and granitic rocks. We propose that the intrusion of an oxidized, Fe- and Cu-rich basic magma into a partially crystallized acid magma resulted in partial mixing and may have triggered the abrupt separation of an iron-oxide-rich melt. Our results highlight the importance of magma mixing and metal unmixing, possibly associated with stress relaxation during post-collisional evolution. Supplementary material Electron microprobe analyses of plagioclase in monzonitic rocks, MMEs and electron microprobe analyses of K-feldspar in monzonitic rocks are available at http://www.geolsoc.org.uk/SUP18434.