ENCLAVES IN THE ROCHOVCE GRANITE INTRUSION AS INDICATORS OF THE TEMPERATURE AND ORIGIN OF THE MAGMA

Two boreholes in the Mo-W-bearing porphyric Cretaceous granite, locate d near the Village of Rochovce, Western Carpathians, reveal the existe nce of two types of enclaves: 1. micaceous enclaves (biotite-plagiocla se gneisses without quartz, with highly calcitic plagioclases) and 2. mafic microgranular enclaves (MME), with predominantly dioritic compos ition. In the first type, corundum, Zn-hercynite and magnetite were pr oduced due to the high temperature melting of biotite. These are consi dered to be restites. The melting reactions in biotite indicate that t he granite magma temperatures exceeded 800 degrees C at the time of th e enclave melting. The mafic microgranular enclaves represent portions of mafic magma incorporated in the granitic magma. Seven types of min eralogical-petrological indicators of magma mixing were found. The che mical and Sm/Nd isotopic characteristics of the host granite and MME s how that chemical and isotopic equilibration was achieved within the g ranite-MME system. The initial is an element of Nd value in granite (- 3.0) indicates that some mafic magmatic material was added to the magm a chamber. The apparent crustal residence age (T-DM = 1100 Ma) indica tes an old, Precambrian history of the crustal source material. Thus, the Rochovce magma was derived from a crustal source, with addition of more mafic (probably mantle-derived) magma.