• 责任者：Fu Chenjian (Key Laboratory of Orogenic Belt and Crust Evolution ; Ministry of Education ; School of Earth and Space Sciences ; Peking University ; Beijing 100871 ; China) ; Li Jianghai
• 刊名：Chinese Journal of Geophysics
• 出版年：2013
• 卷期：56(9)
• 关键词：火成岩 ; igneous rocks ; 古板块构造 ; palaeo plate tectonics ; 塔里木板块 ; Tarim Plate
• 页码：p.3061-3070
• 图表：illus., 1 table, 50 refs.
• 分类号：0300
• issnNo：ISSN0001-5733
• isbnNo：CN11-2074/P

     It is difficult to determine longitudes of a paleo-plate for times before ～130 Ma,the age at the end of the oldest hotspot track.In the Early Permian,the Tarim Block is without strong longitudinal constraints.What we know is that the northern margin of the Tarim craton had collided with Kazakhstan by this period.The 290 Ma Tarim Large Igneous Province （TLIP）can help constrain the longitude of the 290 Ma Tarim Block using the Plume Generation Zone （PGZ） method.The PGZ method concludes that because LIP eruption sites all project downward onto the margins of the African ＆ Pacific Large Low Shear Velocity Provinces （LLSVPs） and other smaller,Low Shear Velocity Provinces （LSVPs） at the core-mantle boundary （CMB）,those PGZs have not moved for 300 （even 540） Ma.The 290 Ma TLIP is on the Tarim Block and good paleomagnetic data position it at a certain latitude between 17.6°N and 33.6°N （present-day reference point 39°N,80°E,estimated center for where the plume impinged the lithosphere according to the sedimentary response to the Early to Middle Permian basaltic magmatism） at a time little affected by True Polar Wander （TPW）.If the TLIP erupted above the margins of the LLSVPs,there are five possible longitudinal zones where the 17.6°N to 33.6°N parts of latitude intersects or touches the margins.But the reconstructions with the Tarim LIP erupted above the margins of two LLSVPs would imply unrealistically huge sizes up to 12000～ 18000 km long of Kazakhstan between Baltica and Tarim,and high mean drift rates of Tarim （27～42 mm/a minimum） for the ～290 Ma interval between the Early Permian and the present.In conclusion,the TLIP eruption site is not related to the margins of two LLSVPs.Interestingly,we found that there is a separate,smaller LSVP （20°N,60°E; dVs≈-0.4％ in the SMEAN model of Becker and Boschi （2002） while different negative dVs values in other S-/P-wave velocity anomaly models） near the eastern edge of the African LLSVP,which is just within the latitudinal limits between 17.6°N and 33.6°N and not covered by Pangea either.There is no disagreement with previous geologic data if we reconstruct TLIP above this LSVP.So 20°N,60°E （with a ～5°uncertainty） is the most realistic alternative as the TLIP eruption site.Not only does this positioning determine the previously unknown width of Kazakhstan between Tarim and Baltica,the northeastern part of Pangea （in the Global Hybrid reference frame） at that time,which was as much as 2000 km,but also demonstrates that the TLIP is very similar with the 251 Ma Siberian LIP （SLIP）,whose eruption site also lies vertically above the margin of a separate,small LSVP.This reconstruction of the 290 Ma Tarim Block suggests that the TLIP was probably formed by a deep CMB plume and didn＇t share the same PGZ with the 258 Ma Emeishan LIP （ELIP,related to the Pacific LLSVP suggested） and the SLIP,which is not consistent with previous suggestions about the plume underneath the 290 Ma TLIP may be linked to similar magmatism that formed ELIP and SLIP,if they all generated from the CMB.