A major change in magma sources in late Mesozoic active margin of the circum‐Sea of Japan domain: Geochemical constraints from late Paleozoic to Paleogene mafic dykes in the Sergeevka belt, southern Primorye, Russia

Abstract

More than 30 mafic dykes crop out in the Sergeevka belt in the coastal South Primorye, Far East Russia, of which geologic settings have been unclear for years. This study conducted major-and trace elements characterization, Sr-Nd isotope analyses, and Ar-Ar amphibole and U-Pb zircon datings for these rocks in order to identify their origin. The results demonstrated that all dykes are characterized by high Ba/Yb and low Nb/Y, Zr/Y, and Th/Yb ratios, which suggest their origin from arc melts derived from thin wedge mantle and shallow-dipping slab. These dykes are clearly separated into two distinct age/geochemistry suites; that is, the Paleogene and Early Cretaceous one with dolerites/basalts and adakitic rocks, and the Permian-Triassic one with high-Mg and high-Al gabbro-dolerite varieties. Their geochemistry suggests that the older suite was sourced from a primitive depleted MORB mantle (DMM)-type mantle, whereas the younger suite from an enriched mantle II (EM2)-type mantle domain. The transition in source type from DMM to EM2 occurred during the Jurassic-earliest Cretaceous time, probably by a strong influence of a mantle plume onto the long-continuing subductionrelated magmatism. The plume influence reached the maximum when the unique meimechite-picrite complex formed in the region.

Metallogenic Evolution of Northeast Asia Related to the Cretaceous Turn of Geological Evolution

“…Some plume-related complexes of East Russia, Japan, Northeast China, and Mongolia [8][9][10][11]20] also formed a part of this suite. The more recent tectonic and petrological studies [21][22][23] strongly confirmed this suggestion. The East-Asian Adakitic Province in Figure 2 shows a surficial projection of the plume-flat subduction interaction that provided the anomalous endogenous and metallogenic activities in the region during CTGE.…”

“…The detailed mineralogical, isotopic (Nd, Sr, C, O) and geochemical petrological studies [8,10,23,[25][26][27][28][29][30] clearly identified a deep enriched mantle source of the meimechitepicrite rocks (Figure 6) that is close to the source of the kimberlitic melts. The kimberlitic affinity is especially well manifested by the mineral suite including diamond, picroilmenite, and Ti-rich Cr-spinel (Figure 7).…”

“…The kimberlitic affinity is especially well manifested by the mineral suite including diamond, picroilmenite, and Ti-rich Cr-spinel (Figure 7). Isotopic-geochemical evidence of interaction between mantle plume and subduction in the Sea-of-Japan region (simplified from [23]). (A) Sr-Nd isotopic compositions of the Jurassic-Early Cretaceous mafic-ultramafic and adakitic rocks (after [18]) with addition from [31] for rocks of the Lazurnoe porphyry Cu-Mo (+Au, Ag) deposit.…”

“…The MORB, Mid-Ocean Ridge Basalt; DMM, Depleted Mantle Member; WPB, Within-Plate Basalt; HIMU, EM1, and EM2, enriched mantle sources [33]. [34,35], respectively, for Cr-spinel from the meimechite-picrite complex of Sikhote-Alin (simplified from [23]). MORB, Mid-Ocean Ridge Basalt; OIB, Oceanic Island Basalt; ARC, Arc (subduction-related) basalts; BABB, Back-Arc Basin basalt.…”

“…Figure 7. TiO 2 vs. Cr/(Cr + Al) and Al 2 O 3 diagrams by[34,35], respectively, for Cr-spinel from the meimechite-picrite complex of Sikhote-Alin (simplified from[23]). MORB, Mid-Ocean Ridge Basalt; OIB, Oceanic Island Basalt; ARC, Arc (subduction-related) basalts; BABB, Back-Arc Basin basalt.…”