TY - JOUR

T1 - Mineral Chemistry and Trace Element Composition of Clinopyroxenes from the Middle Cambrian Ust’-Sema Formation Ankaramites and Diopside Porphyry Basalts and the Related Barangol Complex Intrusions, Gorny Altai, Russia

AU - Khlif, Nezar

AU - Vishnevskiy, Andrey

AU - Izokh, Andrey

AU - Chervyakovskaya, Maria

N1 - Funding Information: Funding: The research: except for the LA‐ICP‐MS, was conducted on a state assignment of IGM SB RAS. The LA‐ICP‐MS study was supported by a state assignment from the “Geoanalitik” shared research facilities of IGG UB RAS (No. AAAA‐A18‐118053090045‐8). The re‐equipment and com‐ prehensive development of the “Geoanalitik” shared research facilities of the IGG UB RAS were financially supported by a grant from the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075‐15‐2021‐680). Funding Information: The research: except for the LA-ICP-MS, was conducted on a state assignment of IGM SB RAS. The LA-ICP-MS study was supported by a state assignment from the ?Geoanalitik? shared research facilities of IGG UB RAS (No. AAAA-A18-118053090045-8). The re-equipment and com-prehensive development of the ?Geoanalitik? shared research facilities of the IGG UB RAS were financially supported by a grant from the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075-15-2021-680). Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2022/2

Y1 - 2022/2

N2 - The origin and geodynamic settings of the Ust’-Sema Formation and the Barangol Complex are some of the most controversial issues in the Early Paleozoic history of the Altai–Sayan Fold Belt. The Ust’-Sema Formation volcanic rocks are enriched in high-Ca clinopyroxene phenocrysts and were classified as ankaramites and diopside porphyry basalts. In this work, we first present LA- ICP-MS analyses of the clinopyroxenes, along with studies of the petrography, mineral composition, and whole-rock chemistry of the Ust’-Sema Formation and related Barangol Complex rocks. An LA- ICP-MS clinopyroxene study showed a slight depletion of light rare-earth elements (La/Yb)N = 0.1– 1.0 (on average 0.4); and strong depletion of the high-field-strength elements (Zr, Hf, and Nb) and large-ion lithophile (Rb) elements. An Sr anomaly showed a positive correlation with Mg#. Major-and trace-element composition of the clinopyroxene cores show that these clinopyroxene grains were not captured from the mantle rocks as previously assumed and that the Ust’-Sema Formation and the Barangol Complex rocks were formed from magma with island arc characteristics. The in-creased titanium and light rare-earth element contents in the phenocryst rims from Biyka volcano suggest an active interaction of the ankaramitic magma with rocks or melts of OIB type.

AB - The origin and geodynamic settings of the Ust’-Sema Formation and the Barangol Complex are some of the most controversial issues in the Early Paleozoic history of the Altai–Sayan Fold Belt. The Ust’-Sema Formation volcanic rocks are enriched in high-Ca clinopyroxene phenocrysts and were classified as ankaramites and diopside porphyry basalts. In this work, we first present LA- ICP-MS analyses of the clinopyroxenes, along with studies of the petrography, mineral composition, and whole-rock chemistry of the Ust’-Sema Formation and related Barangol Complex rocks. An LA- ICP-MS clinopyroxene study showed a slight depletion of light rare-earth elements (La/Yb)N = 0.1– 1.0 (on average 0.4); and strong depletion of the high-field-strength elements (Zr, Hf, and Nb) and large-ion lithophile (Rb) elements. An Sr anomaly showed a positive correlation with Mg#. Major-and trace-element composition of the clinopyroxene cores show that these clinopyroxene grains were not captured from the mantle rocks as previously assumed and that the Ust’-Sema Formation and the Barangol Complex rocks were formed from magma with island arc characteristics. The in-creased titanium and light rare-earth element contents in the phenocryst rims from Biyka volcano suggest an active interaction of the ankaramitic magma with rocks or melts of OIB type.

KW - Ankaramites

KW - Clinopyroxene phenocrysts

KW - Diopside-rich rocks

KW - LA-ICP-MS

KW - Ural-Alaskan-type intrusions

UR - http://www.scopus.com/inward/record.url?scp=85122927007&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/6ef41e0a-1284-3ae3-93db-f5b2d3f5340b/

U2 - 10.3390/min12020113

DO - 10.3390/min12020113

M3 - Article

AN - SCOPUS:85122927007

VL - 12

JO - Minerals

JF - Minerals

SN - 2075-163X

IS - 2

M1 - 113

ER -