Publication Date:
2017-01-04
Description:
Cretaceous rocks comparable to mid-oceanic ridge and oceanic island basalts were described in
ophiolite association of the Cape Kamchatskii, Eastern Kamchatka (Fedorchuk et al., 1989). New data
on the composition of these basalts, their spinels, and melt inclusions in them are presented in
this paper. Spinel from olivine–plagioclase basalts corresponds in composition to that of
mid-oceanic ridge tholeiites (Mg# =
0.57−0.82, Cr# = 0.33–0.55, TiO2 = 0.03–0.85 wt %). High-K alkali basalts include less magnesian
and chro- mian (Mg# = 0.57–0.70, Cr# = 0.23–0.30), but Ti-rich (TiO2 = 0.60–0.86 wt %) spinel. Low
Cr# and very low Fe3+ contents of spinel distinguish the studied rocks from island-arc basalts of
Eastern Kamchatka. Melt inclu-
sions in spinel from plagioclase–olivine basalts have tholeiitic low-alkali (Na2O = 0.8–2.5 wt %,
K2O =
0.01−0.09 wt %), high-Ca (CaO = 13–15 wt %), and low-Ti (TiO2 = 0.2–1.2 wt %) composition. Chlorine
con-
centrations are extremely low in the melt inclusions (Cl 〈 0.005 wt %), while S contents are high
(S = 0.12 ±
0.03 wt %). Concentrations of incompatible elements in inclusions (La = 0.3–1.2 ppm, Sr = 27–70
ppm,
Zr = 13–21 ppm) are systematically lower than in typical oceanic tholeiites. The melts are
selectively enriched
in K, Sr, and Ba relative to REE in the N-MORB-normalized trace-element spectra. Participation of
plume com-
ponent in the formation of the Late Cretaceous rift-related basalts of the Pacific Ocean, which are
incorporated
now in ophiolite association of the Cape Kamchatskii, is inferred from indicative rock assemblage
and compo-
sition of primitive melts and spinel.
Type:
Article
,
PeerReviewed
Format:
text
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