Geochemically, synorogenic granites show I-type characteristics and their genesis is related to granulitic metamorphism (Niin 1997), although some authors have treated them together with late-orogenic migmatite
granites (Puura et al.
We analyzed outcrop and drill core sections through stromatic migmatites
(with parallel melt veins) in South Finland, Labrador, and the Estonian crystalline basement and found power law distributions in all cases (see Fig.
Favorable types include: (a) granite which contains abundant small flakes of dark mica, and (b) granite which apparently originated by the conversion of ancient sedimentary rocks of complex composition (sometimes called granitized rocks, migmatites
, and some of the hybrid granites).
geochemical surveys) was carried out within the paragneisses, migmatites
, pegmatites, granites and granodiorites underlying most of the Company's ground position.
The Yaounde series consist of strongly deformed meta-sedimentary rocks and migmatites
(Nzenti et al, 1988)
The crystalline rocks within the DPDZ are granulites, biotite granites and migmatites
, the latter consisting of amphibole-plagioclase palaeo- and mesosomes, and plagioclase-quartz-biotite[+ or -]microcline[+ or -]amphibole neosomes.
The host rocks are highly granitized to cataclastites or migmatites
Kriegsman and Nystrom present a review of melt segregation rates in migmatites
along with a companion paper outlining a detailed case study.
Oyawoye (1972) observed that the Basement Complex consists mainly of quartzofeldspathic migmatites
and gneisses with occasional quartzites, marbles.
The composition of rocks and their metamorphic grade change rapidly from granulitic or high-grade amphibolitic in the PPZ to mainly medium-grade amphibolitic metasediments and intermediate to felsic metavolcanics, migmatites
, and late-orogenic microcline granites in the Tallinn and Alutaguse zones.
The host rocks of the silver mineralization are mainly Archean migmatites
and gneisses and Middle Proterozoic rhyolite, andesite porphyry, and volcanic breccia, which have been intruded by Messozoic granitic stocks.
-gneiss complex is Neo-Proterozoic to Meso-Archean (542Ma-3200Ma) in age and composed of migmatites