Large igneous provinces: crustal structure, dimensions, and external consequences
Large igneous provinces (LIPs) are a continuumof voluminous iron and magnesium rich rockemplacements which include continental flood basaltsand associated intrusive rocks, volcanic passive margins,oceanic plateaus, submarine ridges, seamountgroups, and ocean basin flood basalts. Such provincesdo not...
| Published in: | Reviews of Geophysics |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Amer Geophysical Union
1994
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| Subjects: | |
| Online Access: | https://doi.org/10.1029/93RG02508 http://ecite.utas.edu.au/73827 |
| Summary: | Large igneous provinces (LIPs) are a continuumof voluminous iron and magnesium rich rockemplacements which include continental flood basaltsand associated intrusive rocks, volcanic passive margins,oceanic plateaus, submarine ridges, seamountgroups, and ocean basin flood basalts. Such provincesdo not originate at "normal" seafloor spreading centers.We compile all known in situ LIPs younger than250 Ma and analyze dimensions, crustal structures,ages, and emplacement rates of representatives of thethree major LIP categories: Ontong Java and Kerguelen-Broken Ridge oceanic plateaus, North Atlanticvolcanic passive margins, and Deccan and ColumbiaRiver continental flood basalts. Crustal thicknessesrange from 20 to 40 km, and the lower crust is characterizedby high (7.0-7.6 km s -1 compressionalwave velocities. Volumes and emplacement rates derivedfor the two giant oceanic plateaus, Ontong Javaand Kerguelen, reveal short-lived pulses of increasedglobal production; Ontong Java's rate of emplacementmay have exceeded the contemporaneous global production rate of the entire mid-ocean ridge system. Themajor part of the North Atlantic volcanic province liesoffshore and demonstrates that volcanic passive marginsbelong in the global LIP inventory. Deep crustalintrusive companions to continental flood volcanismrepresent volumetrically significant contributions tothe crust. We envision a complex mantle circulationwhich must account for a variety of LIP sizes, thelargest originating in the lower mantle and smallerones developing in the upper mantle. This circulationcoexists with convection associated with plate tectonics,a complicated thermal structure, and at least fourdistinct geochemical/isotopic reservoirs. LIPs episodicallyalter ocean basin, continental margin, and continentalgeometries and affect the chemistry and physicsof the oceans and atmosphere with enormouspotential environmental impact. Despite the importanceof LIPs in studies of mantle dynamics and globalenvironment, scarce age and deep crustal data necessitateintensified efforts in seismic imaging and scientificdrilling in a range of such features. |
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