TY - JOUR

T1 - High-Alumina Pyroxenite Xenoliths from Quaternary Basalt of Spitsbergen Island: Evidence for Continental Crust Delamination.

AU - Koreshkova, M. Yu.

AU - Marin, Yu. B.

AU - Nikitina, L. P.

AU - Downes, H.

AU - Tokusheva, A.

AU - Goncharov, A. G.

PY - 2019/4/1

Y1 - 2019/4/1

N2 - Abstract: The origin of spinel–garnet pyroxenite from xenoliths in Quaternary basaltoids of Spitsbergen Island (Svalbard Archipelago) is discussed. The rocks have a high concentration of Al 2O 3 and MgO and low Cr. The primary magmatic association Spl–Opx–Cpx and the high Al content in pyroxenes provide evidence for the formation of these rocks as cumulates of hydrous basaltic melts in the lower crust at a pressure of ~1.2 GPa. Transformation of the texture from the magmatic hypidiomorphic to the metamorphic granoblastic and growth of garnet at the expense of spinel and high-alumina pyroxenes indicate transport of rocks to a depth below the spinel/garnet phase transition boundary in the Cr 2O 3-free CaO–MgO–Al 2O 3–SiO 2 system. The parameters of the Grt–Opx equilibrium range within 1060–1120°C and 2.2–2.6 GPa. Thus, magmatic pyroxenite was transported to a great depth into the mantle, which provides evidence for delamination in the region of the lower continental crust containing ultramafic cumulates.

AB - Abstract: The origin of spinel–garnet pyroxenite from xenoliths in Quaternary basaltoids of Spitsbergen Island (Svalbard Archipelago) is discussed. The rocks have a high concentration of Al 2O 3 and MgO and low Cr. The primary magmatic association Spl–Opx–Cpx and the high Al content in pyroxenes provide evidence for the formation of these rocks as cumulates of hydrous basaltic melts in the lower crust at a pressure of ~1.2 GPa. Transformation of the texture from the magmatic hypidiomorphic to the metamorphic granoblastic and growth of garnet at the expense of spinel and high-alumina pyroxenes indicate transport of rocks to a depth below the spinel/garnet phase transition boundary in the Cr 2O 3-free CaO–MgO–Al 2O 3–SiO 2 system. The parameters of the Grt–Opx equilibrium range within 1060–1120°C and 2.2–2.6 GPa. Thus, magmatic pyroxenite was transported to a great depth into the mantle, which provides evidence for delamination in the region of the lower continental crust containing ultramafic cumulates.

UR - http://www.scopus.com/inward/record.url?scp=85066928185&partnerID=8YFLogxK

U2 - 10.1134/S1028334X19040123

DO - 10.1134/S1028334X19040123

M3 - Article

VL - 485

SP - 413

EP - 417

JO - Doklady Earth Sciences

JF - Doklady Earth Sciences

SN - 1028-334X

IS - 2

ER -