|
The North Atlantic Igneous Province (NAIP) is a large igneous province estimated to be at least 1.3 km2 in area and 6.6 km3 in volume.〔 km2 and a volume of flood basalts of 1.8 km3, yielding a mean eruption rate of 0.6 km3/yr or 2.4 km3/yr if two-thirds of the basalts were emplaced within 0.5 m.y. The total crustal volume is 6.6 km3, resulting in a mean crustal accretion rate of 2.2 km3/yr. Thus NAVP ranks among the world's larger igneous provinces if the volcanic margins are considered.}}〕 Geographically, the NAIP makes up all of the North Atlantic Ocean as well as the Paleocene and Eocene basalts of Greenland, Iceland, the United Kingdom, Denmark, Norway and many of the islands located in the north eastern portion of the North Atlantic ocean. Isotopic dating indicates the most active magmatic phase of the NAIP was between ca. 60.5 and ca. 54.5 Ma (million years ago) (mid-Paleocene to early Eocene) - further divided into Phase 1 (pre-break-up phase) dated to ca. 62-58 Ma and Phase 2 (syn-break-up phase) dated to ca. 56-54 Ma. Continuing research also indicates that continental plate movement (Eurasian, Greenland, and North American), that regional rifting events, and that seafloor spreading between Labrador and Greenland may have begun as early as ca. 95-80 Ma, ca. 81 Ma, and ca. 63-61 Ma respectively (late Cretaceous to early Paleocene). The formation of the NAIP has also been linked to the Iceland hotspot / mantle plume. Through both geochemical observations and reconstructions of paleogeography, it is speculated that the present day Iceland hotspot originated as a mantle plume on the Alpha Ridge (Arctic Ocean) ca. 130-120 Ma, migrated down Ellesmere Island, through Baffin Island, onto the west coast of Greenland, and finally arrived on the east coast of Greenland by ca. 60 Ma. The present-day Iceland and Jan Mayen hotspots and North Atlantic Ridge are still geologically active. The NAIP is made up of both onshore and offshore basalt floods, sills, dykes, and plateaus. Dependent upon various regional locations, the NAIP is made up of MORB (Mid Ocean Ridge Basalt), alkali basalt, tholeiitic basalt, and picrite basalt. Synonymous or related names *Brito-Arctic province (BAP) * North Atlantic Tertiary Province (NATP) * North Atlantic Volcanic Province (NAVP) * North Atlantic Basalt Province (NABP) * North Atlantic Tertiary Volcanic Province (NATVP) * British Tertiary Igneous Province (BTIP) * British Tertiary Volcanic Province (BTVP) * British Paleogene Igneous Province (BPIP) *Thulean Plateau ==See also== *Igneous rock *Geologic province *Mantle plume *Hotspot *Oceanic plateau *Continental flood basalt *Large igneous province *Dike swarm 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「North Atlantic Igneous Province」の詳細全文を読む スポンサード リンク
|