Petrography, Geochemistry and Rock Association Affinity of Dolerites of the Bobrynets Dyke Belt (Ingul Terrain of the Ukrainian Shield)
UDC 552.333.4 : (552.08 + 550.4 + 551.22) (477)
https://doi.org/10.15407/mineraljournal.37.01.056
A.V. Mitrokhin (1), L.V. Shumlyanskyy (2), E.A. Vishnevskaya (1)
(1) Taras Shevchenko Kyiv National University
90, Vasylkivska Str., Kyiv, Ukraine, 03022
Е-mail: mitrokhin.a.v@yandex.ua; genyvishnevskia@mail.ru
(2) M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of NAS of Ukraine
34, Acad. Palladina Pr., Kyiv-142, Ukraine, 03680
Е-mail: lshumlyanskyy@yahoo.com
Petrography, Geochemistry and Rock Association Affinity of Dolerites of the Bobrynets Dyke Belt (Ingul Terrain of the Ukrainian Shield)
Language: Russian
Mineralogical journal 2015, 37 (1): 56-68
Abstract: The objects of research are non-metamorphized basic dykes of the Bobrynets Dyke Belt (BDB) intruded into the Paleoproterozoic crystalline basement of the Ingul terrain of the Ukrainian Shield. The goal, data and methods of research. Specification of geological position of the BDB, detection of mineralogical, petrographical and geochemical features of dyke rocks as well as clarification of their affinity for certain petrographical association were the purposes of researches. The core samples were studied using optical and electron microscopy, the electron probe microanalysis, XRF and ICP-MS methods. Obtained results and conclusions. Authors established the prevalence of non-metamorphized olivine dolerites within the BDB. Mode of occurrence, microtextural features and composition allow their identification as hypabyssal members of the Precambrian dolerite-diabase association. This association is a paleoanalogue of the continental plateau basalt association of the Phanerozoic. The most prominent petrographic features of the BDB dolerites are: 1) their cainotypic character; 2) holocrystalline aphyric or microporphyric textures; 3) high but variable Ca in the plagioclase: An51—83 in the phenocrysts and An41—67 in the groundmass; 4) simultaneous occurrence of pigeonite Wo8—15En53—67 and augite Wo28—38En37—54; 5) high but variable Mg in pyroxene and olivine; 6) Ti-magnetite-ilmenite association of ore minerals. Studied dolerites are low alkaline basic rocks relevant to tholeiitic series. The initial values ɛ Nd1800 = +0.7—0.9 and 87Sr/86Sr = 0.70274—0.70381 testify to moderately depleted mantle source. Model Nd ages of magmatic source are TDM = 2.37—2.41 and TCHUR = 1.64—1.67 Ga. Practical value of the BDB dolerite-diabase association can be defined by potential Cu-Ni specialization of many known dolerite-diabase complexes.
Keywords: petrology, dyke rock, dolerites, Ukrainian Shield.
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