granitoid complex
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2020 ◽  
Vol 55 (8) ◽  
pp. 1561-1580
Author(s):  
Tapio Halkoaho ◽  
Marjaana Ahven ◽  
O. Tapani Rämö ◽  
Janne Hokka ◽  
Hannu Huhma

Abstract The Kiviniemi mafic intrusion, near the eastern margin of the Paleoproterozoic Central Finland Granitoid Complex, is both spatially and temporally associated with post-kinematic Fe-Ti-P-enriched Svecofennian orogenic mafic magmatism. The main rock types in this small (~ 15 ha) intrusion are garnet-bearing fayalite ferrodiorite, leucoferrodiorite, ferromonzodiorite, and pyroxene diorite. The garnet-bearing fayalite ferrodiorite and leucoferrodiorite contain 50–281 ppm Sc, 275–5600 ppm Zr, and 58–189 ppm Y (n = 42), delineating a mineralized deposit some 2.5 ha in extent. Overall, these rocks show an evolved (iron-enriched) tholeiitic character; low values of Ni (< 20–40 ppm), Cr (< 20 ppm), and Cu (< 20–80 ppm); and high contents of Zn (213–700 ppm). The rock-forming minerals in the ferrodioritic rocks are (ferro)hedenbergite, plagioclase (~ An40), ferropargasite and ferroedenite, almandine garnet, and fayalite (Fo1–4). Accessory minerals include zircon, ilmenite, fluorapatite, biotite, pyrite, pyrrhotite, potassium feldspar, grunerite, and clinoferrosilite. Some relict cumulate textures have been preserved, but primary magmatic features have largely been overprinted by strong recrystallization and corona formation. The main carriers of Sc are amphibole, clinopyroxene, and apatite. The remarkably strong enrichment of Sc in ferromagnesian silicates and apatite, rather than in specific Sc-minerals, implies magmatic enrichment. Post-kinematic mafic intrusions in central Finland constitute a bimodal association with co-existing granitoid counterparts. The Kiviniemi mafic intrusion is associated with a coarse megacrystic granite and the two rock type display mingled contacts, indicative of contemporaneity of the two magmas. This conclusion is in accord with the coincident U-Pb zircon ages for the ferrodiorite, at 1857 ± 2 Ma (multigrain ID-TIMS) and the megacrystic granite, at 1860 ± 7 Ma (single-crystal LA-MC-ICP-MS). The initial εNd value of the ferrodiorite and the granite are + 0.1 and − 2.5, respectively. These Nd isotope compositions probably reflect a chondritic mantle source for the ferrodiorite and suggest incorporation of some Archaean crustal material into the granite in the course of magmatic evolution. The resource estimation calculated for Kiviniemi intrusion by using 40 g/t Sc cut off value is 13.4 Mt of rock with an average grade of 162.7 g/t scandium, 1726 g/t zirconium, and 81 g/t yttrium.


2019 ◽  
Vol 128 (1B) ◽  
pp. 21
Author(s):  
Nguyễn Thị Thủy ◽  
Nguyễn Thị Lệ Huyền ◽  
Nguyễn Thị Ngọc Trâm ◽  
Lê Hải Nghĩa

The Khe Phen granite quarry located in Huong Tra district (Thua Thien Hue province) has been confirmed as a part of the Ba Na granitoid complex (G/K<sub>2</sub><em>bn</em>), mostly composed of two-mica granite and porphyritic granite. Field survey data show that the granites here are cut across by five distinct narrow dikes (about 50-70 cm wide) including granite pegmatite, granite aplite, aplite, granodiorite and lamprophyre diorite. Mineral compositions of the granite pegmatite and aplite dikes are similar with those of the host granite, which are mainly comprised of quartz (27-35 %), orthoclase (45-58 %), plagioclase (4-15 %), biotite (1-3 %) and a few opaque minerals. Meanwhile, the granodiorite and lamprophyre diorite dikes are melanocratic and compositionally much more mafic, particularly lamprophyre diorite, evidenced by a presence of hornblende (50-55 %), plagioclase (33-40 %), quartz (3-15 %), calcite (5-17 %)... Origin and emplacement age of the latter dikes have not been reported so far, and thus are needed for further studies based on geochemical and isotopic data.


2019 ◽  
Vol 2 (1) ◽  
pp. 96-101
Author(s):  
Tran Van Thanh ◽  
Pham Trung Hieu

Muong Lat granitoid complex located in Thanh Hoa province. It is composed of two mica granite, aplite and pegmatoid. Rock forming minerals include mainly K-feldspar, quartz biotite and muscovite. Crystallization age of pegmatite in Muong Lat body is determined by U-Pb zircon LA-ICP-MS method. Most of the analytical results 206Pb age / 238U ranged from 217–238 Ma, average 230 ± 7 Ma. Age results indicate, the existence magma activity in the study area. Three inherited zircon core gaves age of ~2.8Ga, ~2.4Ga, ~1.8Ga, ~400Ma and ~750 Ma, suggesting that the continental crust of the study area including material composition of the Neoarchean, Paleoproterozoic, Paleozoic and Neoproterozoic


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