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Phanerozoic Androgenic Magmatism
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
The basalt–dolerite assemblage is represented by the Pripyat–Donets dyke swarm which is well developed over the entire area of the DDP; it is composed of tholeiitic non-differentiated basalts. The trachybasalt–trachyandesite–trachyrhyolite assemblage comprises high-Ti moderately alkaline differentiated series with basalts predominant, together with highly acid variaties. An assemblage of melanephelinite, alkaline ultramafic and gabbroids is developed at the base of the section. It comprises a differentiated alkaline series, including high-Ti picrites, limburgites, augitites, basanites, analcime basalts, trachytes, alkali trachytes, meimechites, phonolites, nephelinites, leucitites, tephrites and their tuffs, and carbonatites. The last assemblage (of alkali basites and phonolites) is very similar in all of its parameters to that of melanephelinite, differing only in its more leucocratic composition, with nephelinites and trachytes being predominant. The trachybasalt–trachyrhyolite assemblage is found up section, being composed of a high-Ti, moderately alkaline differentiated series with predominant basalts and acid varieties.
The Breznik epithermal Au occurrence, Western Srednogorie - Bulgaria: an “atypical” (?) low-sulphidation hydrothermal system
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
J. Crummy, I. Mutafchiev, I. Velinov, R. Petrunov
The Breznik Au occurrence is formed in an Upper Cretaceous volcano-intrusive structure. The volcano is an evidence of demonstrably extrusive multiphase activity and is developed in a linear magma-conducting zone, resulting from the intersection of deep, 120° and 70° trending faults (Panayotov et al., 1982). The central part of the structure is made up of agglomeratic and coarse-blocked volcanoclastic rocks with andesitic, trachyandesitic and trachybasaltic fragments with clastlava interbeds. Two types of dyke bodies cut the above rocks – fine Porphyric ones of basaltic composition and coarse Porphyric ones of gabbrodioritic composition. The margin of the structure is made up of thick tephroidal flysch (tuffs, tuffites, marls, sandstones) that host a trachyandesitic body. A massive Porphyric body of gabbrodioritic composition was identified at 300-350m depth beneath the present surface of the central part of the structure. It shows E-W orientation along strike and dips to the south. Its configuration is documented by gravity data, uralitisation processes in the exocontact parts and isolated drill intersections. Hydrothermal processes are controlled by palaeotectonic dislocations, generally of an E-W trend, character-rising the extension of the structure and most likely associated with the intrusion of the massive body.
Geochemistry of seafloor surface sediment and submarine hydrothermal signature of Tomini Bay, Indonesia
Published in Australian Journal of Earth Sciences, 2022
A. Yuliyanti, H. Permana, I. Setiawan, H. Nurohman, S. Purwo Saputro
The youngest sediment sequence in Tomini Basin comprises terrigenous sediments sourced from the west area, volcanic components of explosive acid volcanic material sourced from the north and Pliocene volcanic tuffs that are mainly proximal to Togian Island. The Togian Island is a product of Plio-Pleistocene volcanism with medium-K to shoshonitic magma affinity of basaltic-trachyandesite to trachydasite volcanism. Pliocene magmatism on Togian Island is hypothesised to be the product of crustal thinning and mantle melting beneath Tomini Bay and Pleistocene–Recent volcanic activity of Una-Una (Pholbud et al., 2012). The Quarternary Una-Una Volcanic rocks were classified as trachyandesite and trachydacite, with moderate–high SiO2 (56.79–64.33 wt%), low MgO (1.70–2.74 wt%), high Na2O (4.50–5.44 wt%) and low TiO2 (0.30–0.54 wt%) contents (Sendjaja et al., 2020).
Delineation of geochemical anomalies for mineral exploration using combining U-statistic method and fractal technique: U-N and U-A models
Published in Applied Earth Science, 2022
Seyyed Saeed Ghannadpour, Ardeshir Hezarkhani
The late Eocene is generally comprised of volcanic rocks which have been described chronologically as follows: (I) andesitic basalts (II) red tuffs and tuff sediments (III) trachyandesite and trachybasalt rocks; (IX) tuff and tuff sandstone (X) trachyandesite and trachybasalts along with basaltic lavas and agglomerate; (XI) porphyritic rocks having phenocrysts of plagioclase, monoclinic pyroxene and olivine and a matrix of plagioclase, pyroxene, feldspar and microliths.