New constraints on the age and evolution of the Wishbone Ridge, southwest Pacific Cretaceous microplates, and Zealandia-West Antarctica breakup
New constraints on the age and evolution of the Wishbone Ridge, southwest Pacific Cretaceous microplates, and Zealandia-West Antarctica breakup
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DOI：
10.1130/g22168.1
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发表时间：
2006-03
期刊：
影响因子：
5.8
通讯作者：
N. Mortimer;K. Hoernle;F. Hauff;J. Palin;W. Dunlap;R. Werner;K. Faure
中科院分区：
文献类型：
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作者：
N. Mortimer;K. Hoernle;F. Hauff;J. Palin;W. Dunlap;R. Werner;K. Faure
我们目前的分析结果，从四个疏浚位置在东西兰迪亚大陆边缘和邻近的洋壳。115 Ma英安岩疏浚西Wishbone岭（WWR）同位素原始，弱埃达克质，板状熔岩。97马A型花岗岩和玄武岩从最东端的查塔姆隆起扩大了已知的地区后俯冲冈瓦纳岩浆活动。来自查塔姆隆起南部断块的角闪岩级片岩为西兰迪亚和西南极带的侏罗纪-白垩纪增生棱柱岩提供了重要桥梁。WWR作为115 Ma洋内俯冲系统的残余物的新认识意味着WWR作为断裂带或扩张脊的先前假设需要修改。英安岩年龄限制奥斯伯恩海槽扩张，导致Hikurangi-Manihiki火成岩高原的解体，开始前115马。我们推测，在115 Ma后，WWR是由一个洋内扩张中心，发展沿着其东南侧裂谷。这个扩张中心对冈瓦纳大陆边缘的撞击导致了广泛的95-100 Ma后俯冲岩浆活动，岩石圈拉伸的变化，并最终导致西兰迪亚和西南极洲大陆分裂穿过基底趋势。
We present analytical results from four dredge locations across the eastern Zealandia continental margin and adjacent ocean crust. The 115 Ma dacites dredged from the West Wishbone Ridge (WWR) are isotopically primitive, weakly adakitic, slab-derived lavas. The 97 Ma A-type granites and a basalt from the easternmost Chatham Rise enlarge the known area of postsubduction Gondwana magmatism. Amphibolite-grade schists from a fault block south of the Chatham Rise provide a critical bridge between the Zealandia and West Antarctica belts of Jurassic–Cretaceous accretionary prism rocks. The new recognition of the WWR as a remnant of a 115 Ma intraoceanic subduction system means that previous hypotheses of the WWR as a fracture zone or spreading ridge require modification. The dacite ages constrain the start of Osbourn Trough spreading, which caused breakup of the Hikurangi-Manihiki igneous plateau, to before 115 Ma. We speculate that, after 115 Ma, the WWR was rifted by an intraoceanic spreading center that developed along its southeast side. Impingement of this spreading center against the Gondwana margin led to widespread 95–100 Ma postsubduction magmatism, variable lithospheric stretching, and ultimately continental splitting of Zealandia and West Antarctica across basement trends.