Comparison of petrology and isotope geochemistry of the Bulka peridotite–gabbro massif and granitoids of the Kyzykchadra complex (West Sayan)

• Published in: Geochemistry international Vol. 54; no. 4; pp. 321 - 345
• Main Authors: Borodina, E. V., Izokh, A. E., Mongush, A. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.04.2016; Springer Nature B.V
• Subjects: Depletion; Earth and Environmental Science; Earth Sciences; Geochemistry; Isotopes; Magma; Mantle; Massifs; Petrology; Raw materials; Rocks; Studies; Trace elements; rare-earth elements; layered intrusions; granitoids; peridotite–gabbro complexes; isotopy
• ISSN: 0016-7029; 1556-1968
• DOI: 10.1134/S0016702916040029

The study provides new petrologic and isotope geochemical data for rocks of the 465 ± 5 Ma Bulka massif (Borodina et al., 2011). The primary amphibole from granitoid stocks cutting across the layered series of the massif yielded an Ar–Ar age of 415.9 ± 3.7 Ma. The rocks of the Bulka massif have 143 Nd/ 144 Nd ratio of 0.513243 and εNd (Т) values of +12.00. The granitoids have 143 Nd/ 144 Nd ratios between 0.512919 and 0.512961 and εNd (Т) values between +8.03 and +9.25. The Nd isotope composition indicates that the rocks of the Bulka massif and granitoids were derived from a depleted mantle source. Depletion of the rocks of the massif in LILE, LREE, and HFSE over LILE is inherited from the mantle source, which has geochemical signatures of N-MORB and subduction-related components. Granitoids are metaluminous I-type granites, which were probably generated either by differentiation of intermediate to mafic mantle-derived magmas or by melting of metabasites. The rocks of the granitoid stocks are characterized by enrichment in LILE and LREE and depletion in HFSE over LILE, which suggests derivation from arc-related parental magmas.