Longitude of the Ca.290 Ma Tarim Block: Constraint from the Tarim Large Igneous Province of NW China
详细信息   
摘要

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     man">It is difficult to determine longitudes of a paleo-plate for times before man’; mso-hansi-font-family: ’times new roman’">～man">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 man’; mso-hansi-font-family: ’times new roman’">（man">TLIPman’; mso-hansi-font-family: ’times new roman’">）man">can help constrain the longitude of the 290 Ma Tarim Block using the Plume Generation Zone man’; mso-hansi-font-family: ’times new roman’">（man">PGZman’; mso-hansi-font-family: ’times new roman’">）man"> method.The PGZ method concludes that because LIP eruption sites all project downward onto the margins of the African man’; mso-hansi-font-family: ’times new roman’">＆man"> Pacific Large Low Shear Velocity Provinces man’; mso-hansi-font-family: ’times new roman’">（man">LLSVPsman’; mso-hansi-font-family: ’times new roman’">）man"> and other smaller,Low Shear Velocity Provinces man’; mso-hansi-font-family: ’times new roman’">（man">LSVPsman’; mso-hansi-font-family: ’times new roman’">）man"> at the core-mantle boundary man’; mso-hansi-font-family: ’times new roman’">（man">CMBman’; mso-hansi-font-family: ’times new roman’">）man">,those PGZs have not moved for 300 man’; mso-hansi-font-family: ’times new roman’">（man">even 540man’; mso-hansi-font-family: ’times new roman’">）man"> Ma.The 290 Ma TLIP is on the Tarim Block and good paleomagnetic data position it at a certain latitude between 17.6man’; mso-hansi-font-family: ’times new roman’">°man">N and 33.6man’; mso-hansi-font-family: ’times new roman’">°man">N man’; mso-hansi-font-family: ’times new roman’">（man">present-day reference point 39man’; mso-hansi-font-family: ’times new roman’">°man">N,80man’; mso-hansi-font-family: ’times new roman’">°man">E,estimated center for where the plume impinged the lithosphere according to the sedimentary response to the Early to Middle Permian basaltic magmatismman’; mso-hansi-font-family: ’times new roman’">）man"> at a time little affected by True Polar Wander man’; mso-hansi-font-family: ’times new roman’">（man">TPWman’; mso-hansi-font-family: ’times new roman’">）man">.If the TLIP erupted above the margins of the LLSVPs,there are five possible longitudinal zones where the 17.6man’; mso-hansi-font-family: ’times new roman’">°man">N to 33.6man’; mso-hansi-font-family: ’times new roman’">°man">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 12000man’; mso-hansi-font-family: ’times new roman’">～man"> 18000 km long of Kazakhstan between Baltica and Tarim,and high mean drift rates of Tarim man’; mso-hansi-font-family: ’times new roman’">（man">27man’; mso-hansi-font-family: ’times new roman’">～man">42 mm/a minimumman’; mso-hansi-font-family: ’times new roman’">）man"> for the man’; mso-hansi-font-family: ’times new roman’">～man">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 man’; mso-hansi-font-family: ’times new roman’">（man">20man’; mso-hansi-font-family: ’times new roman’">°man">N,60man’; mso-hansi-font-family: ’times new roman’">°man">E; dVsman’; mso-hansi-font-family: ’times new roman’">≈man">-0.4man’; mso-hansi-font-family: ’times new roman’">％man"> in the SMEAN model of Becker and Boschi man’; mso-hansi-font-family: ’times new roman’">（man">2002man’; mso-hansi-font-family: ’times new roman’">）man"> while different negative dVs values in other S-/P-wave velocity anomaly modelsman’; mso-hansi-font-family: ’times new roman’">）man"> near the eastern edge of the African LLSVP,which is just within the latitudinal limits between 17.6man’; mso-hansi-font-family: ’times new roman’">°man">N and 33.6man’; mso-hansi-font-family: ’times new roman’">°man">N and not covered by Pangea either.There is no disagreement with previous geologic data if we reconstruct TLIP above this LSVP.So 20man’; mso-hansi-font-family: ’times new roman’">°man">N,60man’; mso-hansi-font-family: ’times new roman’">°man">E man’; mso-hansi-font-family: ’times new roman’">（man">with a man’; mso-hansi-font-family: ’times new roman’">～man">5man’; mso-hansi-font-family: ’times new roman’">°man">uncertaintyman’; mso-hansi-font-family: ’times new roman’">）man"> 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 man’; mso-hansi-font-family: ’times new roman’">（man">in the Global Hybrid reference frameman’; mso-hansi-font-family: ’times new roman’">）man"> 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 man’; mso-hansi-font-family: ’times new roman’">（man">SLIPman’; mso-hansi-font-family: ’times new roman’">）man">,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 didnman’; mso-hansi-font-family: ’times new roman’">＇man">t share the same PGZ with the 258 Ma Emeishan LIP man’; mso-hansi-font-family: ’times new roman’">（man">ELIP,related to the Pacific LLSVP suggestedman’; mso-hansi-font-family: ’times new roman’">）man"> 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.

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