|
|||||
|
|
Geochemistry and spatial distribution of OIB and MORB in A’nyemaqen ophiolite zone: Evidence of Majixueshan ancient ridge-centered hotspot |
|
| Authors: | Guo AnLin Zhang GuoWei Sun YanGui Zheng JianKang Liu Ye Wang JianQi |
| Institution: | 1. National Key Lab of Continental Dynamics, Northwest University, Xi'an 710069, China 2. National Key Lab of Continental Dynamics, Northwest University, Xi'an 710069, China;Qinghai Institute of Geological Survey, Xining 810012, China 3. Qinghai Institute of Geological Survey, Xining 810012, China |
| Abstract: | The mafic volcanic association is made up of OIB, E-MORB and N-MORB in the A’nyemaqen Paleozoic ophiolites. Compared with the same type rocks in the world, the mafic rocks generally display lower Nb/U and Ce/Pb ratios and some have Nb depletion and Pb enrichment. The OIB are LREE-enriched with (La/Yb)N = 5−20, N-MORB are LREE-depleted with (La/Yb)N = 0.41−0.5. The OIB are featured by incompatible element enrichment and the N-MORB are obviously depleted with some metasomatic effect, and E-MORB are geochemically intermediated. These rocks are distributed around the Majixueshan OIB and gabbros in a thickness greater than a thousand meters and transitionally change along the ophiolite extension in a west-east direction, showing a symmetric distribution pattern as centered by the Majixueshan OIB, that is, from N-MORB, OIB and E-MORB association in the Dur’ngoi area to OIB in the Majixueshan area and then to N-MORB, OIB and E-MORB assemblage again in the Buqingshan area. By consideration of the rock association, the rock spatial distribution and the thickness of the mafic rocks in the Majixueshan, coupled with the metasomatic relationship between the OIB and MORB sources, it can be argued that the Majixueshan probably corresponds to an ancient hotspot or an ocean island formed by mantle plume on the A’nyemaqeh ocean ridge, that is the ridge-centered hotspot, tectonically similar to the present-day Iceland hotspot. Supported by the National Natural Science Foundation of China (Grant Nos. 40234041 and 40572138) |
| Keywords: | A'nyemaqen ophiolite zone OIB N-MORB and E-MORB association spatial distribution Majixueshan ridge-centered hotspot metasomatism mantle plume |
| 本文献已被 万方数据 SpringerLink 等数据库收录！ | |