L. Hrasko et al., ENCLAVES IN THE ROCHOVCE GRANITE INTRUSION AS INDICATORS OF THE TEMPERATURE AND ORIGIN OF THE MAGMA, Geologica Carpathica, 49(2), 1998, pp. 125-138
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.