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

Citation
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
Citations number
60
Categorie Soggetti
Geosciences, Interdisciplinary
Journal title
ISSN journal
13350552
Volume
49
Issue
2
Year of publication
1998
Pages
125 - 138
Database
ISI
SICI code
1335-0552(1998)49:2<125:EITRGI>2.0.ZU;2-R
Abstract
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.