Petrological Features of the Burlakski and Nizhne-Derbinsk Mafic-Ultramafic Plutons (East Sayan Mountains, Siberia, Russia)

Minerals

Giovanni Grieco¹  Alexey Chernishov²  Alexander Marfin³  Tamara Yakich⁴  Olesya Savinova⁴  Timofey Timkin⁴  Matthew Brzozowski⁵ 

[1] Department of Earth Sciences, Università degli Studi di Milano, via Botticelli 23, 20122 Milan, Italy;Department of Petrography, National Research Tomsk State University, 36 Lenin Ave., 634050 Tomsk, Russia;Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, 664033 Irkutsk, Russia;School of Earth Sciences and Engineering, Division for Geology, Tomsk Polytechnic University, 634050 Tomsk, Russia;State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;

关键词: mafic-ultramafic plutons;    mineral chemistry;    olivine;    pyroxene;    hornblende;    chromian spinel;   

DOI  :  10.3390/min10020119

来源: DOAJ

【 摘 要 】

The Nizhne-Derbinsk mafic-ultramafic complex is located between the Central Asian Orogenic Belt and the Siberian Craton and, is associated with the Ballyk fault. The largest, spatially related to each other, plutons in the central part of the complex are the Burlakski and Nizhne-Derbinsk. Rocks in the main units of these plutons are divided into three groups: peridotites (ultramafic), pyroxenites (sub-ultramafic), and gabbroic rocks (mafic). The ultramafic and sub-ultramafic cumulate series are devoid of plagioclase and contain <3 vol. % chromian spinel. The Fo content of olivine in the sub-ultramafic cumulates from both plutons ranges from Fo79 to Fo86. The En content [= Mg/(Mg + Fe + Ca) × 100 atomic ratio] of clinopyroxenes and orthopyroxenes varies from 46−56, and 63−80, respectively. Plagioclase corresponds to labradorite with An contents between 55 and 57. Hornblende is compositionally similar to pargasite. The sequence of change of rock units corresponds to the paragenesis: olivine − olivine + clinopyroxene (orthopyroxene) − clinopyroxene + orthopyroxene − clinopyroxene + orthopyroxene + plagioclase − orthopyroxene. Petrographic, mineralogical, and mineral chemical features of the Burlakski and Nizhne-Derbinsk plutons suggest that the diversity of the material composition of these plutons is due to the processes of magmatic differentiation in deep-seated conditions. Estimates of crystallization pressures and temperatures of the Burlakski and Nizhne-Derbinsk plutons suggest that they crystallized at high pressures ≥ 10kb and temperatures ranging from 1000−1400 °C. Mineralogical and petrological features suggest that the mafic-ultramafic cumulates were derived from a high-Mg basaltic magma. The presence of magmatic hornblende and hydrous mineral assemblages within the ultramafic cumulates indicates that the parental melts had been enriched in dissolved volatile constituents. Taking into account the age of the gabbronorites of the Burlakski pluton (~490 ± 11.8 Ma), the magmatism likely occurred during the Ordovician collision stage of the evolution of the Central Asian Fold Belt.

【 授权许可】

Unknown