Can plate tectonic processes and perisphere explain the origin of the OJP?
Non-plume enthusiasts have suggested mechanisms for the origin of large igneous provinces that include focusing of melt flow, unusually fertile mantle (see also PT Processes page), large-scale melt ponding, “EDGE” and rift-related processes (see also EDGE page), and a partially molten shallow mantle (e.g., Anderson, 1998). The plate-separation hypothesis (e.g., Anderson et al., 1992; Smith & Lewis, 1999) posits an extensive layer of shallow, volatile-rich, near-solidus, OIB-like (but not plume derived) asthenosphere (“perisphere”) to have resided beneath a region of the Pacific lithosphere that was rifted suddenly by a ridge jump around 120 Ma, causing cataclysmic melting. However, the pre-120 Ma seafloor within several hundred kilometers of the OJP is not much older than the plateau itself, having been formed only ~ 2 – 35 m.y. earlier (e.g., Taylor, 1978; Nakanishi et al., 1992). Thus, during this period, a spreading system was not too distant from the (future) location of the OJP. I
