[SIT32-P03] Meteorite Impact Origin of Mantle Plumes Growing Downward by Mantle Depletion of Volatiles Not Convection From CMB
キーワード：Yellowstone Hotspot、 Impact Volcanism 、Volatile Depletion、Siberian hotspot tracks、Challenger Deep、Warmspot
The origin of Mantle Plumes has remained uncertain until now. Here, we present evidence of meteorite impact origin, based upon our prime example, the Yellowstone hotspot and Columbia River Basalt large igneous province LIP. The hotspot is shallow, only 200 km deep, invalidating a theory of mantle plume origin. The hotspot track runs from the Yellowstone National Park in NW Wyoming, back in time, to the volcanic Modoc Plateau in NE California. We present evidence of apparent remnants of an impact crater existing in the Modoc, a large multi-ring structure at least 160 km diameter. Much of this complex crater has become obliterated by later Cascadia and Sierra orogenies. The crater has a tall 4,100 foot non-igneous central uplift cone, locally known as Chalk Mountain, consisting of diatomaceous earth, presumably the rebound cone of a thin-crust meteorite impact at the Miocene cratonic margin. This falsifies a theoretical prohibition of cosmic impact volcanism. Based on recent insights into explosive volcanism a plausible mechanism based upon mantle depletion of dissolved volatiles is proposed for how meteorite impacts can lead to resurgent calderas of the Yellowstone type and apparent LIP origin from thin crust ET impacts, invalidating theoretical constructs of mantle plumes. Another example of cardinal importance for planet Earth biosphere endurance and survival is a pair end-Permiian comet impacts in the South Kara Sea and the West Siberian basin, apparently fragments of the same giant comet or Edgeworth–Kuiper belt object. Very possibly other fragments of the same body have impacted at times near the Permo-Triassic transition, as the Emeishan LIP in Sichuan, China. The reason is that comets have a fragile nature, being weakly consolidated by gravitational accretion around metal cores, as seen in the Norilsk nickel mine, exploiting the metal core of the S Kara Sea impactor, analogous to the Sudbury, Ontario astrobleme. A hotspot track results from the initial magma chamber, excavated by teraton or even petaton TNT equivalent impact explosions, with deep mantle pentration by tens of km in thin oceanic crust. Here, the S Kara Sea impact initiated the continental extension of the Emperor-Hawaii sea mount chain, Mt Kilauea atop the remnant hotspot. The analogous W Siberian plane hotspot track exits mainland Asia at Sachalin Island, and continues on through Japan to the Marianas ending at the Challenger Deep, Fig. 1. In this case, unlike the S Kara Sea-Hawaii hotspot track, where the metal core remained in the crust at or near the impact site, the core penetrated the crust completely and sank into the mantle. The great depth of the Challenger Deep is due to the large weight of the metal core mass, still sinking deeper now, as can be seen from the GPS continental drift directions world-wide converging upon the Pacific region near Guam. For a continental impact such as Chicxulub on the Yukatan penisula, the impact may excavate only to the Moho, with a plutonic warmspot as the result instead of a volcanic hotspot. The Greater Antilles mark the warmspot track by their granitic basements beneath Tertiary limestones, except in terminal Virgin Gorda, where granite rocks famously form the popular "Baths" at the surface, the warmspot having joined the volcanic arc of the Lesser Antilles.