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• 关键词：Woodlark basin ; Leg 180 ; Dolerites
• 刊名：Trends in Cardiovascular Medicine
• 出版年：2008
• 出版时间：April 2008
• 年：2008
• 卷：18
• 期：3
• 页码：A2
• 全文大小：57 K

文摘

The Moresby Seamount located in the Woodlark Basin is a fragment of oceanic crust (dolerites and gabbros) generated 66.4 ± 1.5 My ago before being obducted during the Eocene on the Australian margin. Since 8 My, the motion of a normal fault related to the opening of the Woodlark Basin is responsible for the unroofing of the Moresby seamount. The latter was sampled during the ODP campaign Leg 180 in 1998. Geochemical compositions of dolerites can be explained by a process of fractional crystallization in which the magnesian spinel was involved. Therefore fractionation processes took place at relatively high pressure (>1 GPa), most likely during the upward migration of deep magmas throughout the mantle. The Fe-rich gabbros, more differentiated than the dolerites, could have derived from an early differentiated magma evolving in the crust at relatively low pressures. The trace element content of dolerites indicates that their source was a depleted oceanic mantle slightly influenced by arc-related magmas. This study suggests that the ophiolites fragment of the Moresby seamount was created in the vicinity of a subduction zone; this model being in agreement with the regional tectonic setting of SE Asian since the Cainozoic.