Origin of volcanism on the flanks of the Pacific‐Antarctic ridge between 41°30′S and 52°S
Origin of volcanism on the flanks of the Pacific‐Antarctic ridge between 41°30′S and 52°S
复制标题
南纬 41°30′ 至 52°之间太平洋-南极海脊两侧的火山活动起源
DOI：
10.1029/2008gc002350
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发表时间：
2009
期刊：
影响因子：
3.7
通讯作者：
H. Guillou
中科院分区：
文献类型：
--
作者：
A. Briais;H. Ondréas;F. Klingelhoefer;L. Dosso;C. Hamelin;H. Guillou
非热点、板内火山活动是东太平洋隆起或太平洋-南极脊附近的共同特征。火山脊和海山链长数十至数百公里，沿脊轴线不对称分布，大部分火山特征发生在太平洋板块。它们的起源仍有争议。我们分析了太平洋-南极脊附近的离轴火山脊，这些数据来自太平洋-南极2号巡航的测深、后向散射、重力和地球化学数据。在这些构造上采集的样品的K/Ar测年显示，火山和下面地壳之间的对比高达3 Ma。声纳图像中强烈的后向散射表明，火山活动似乎仅限于年龄小于3 Ma的海底区域。所有被调查的梅纳德变换断层（TF）以北的脊都显示出最近在脊轴附近的活动，并且不受断层的影响。梅纳德断裂带以南的离轴火山脊在其中心显示出最近的火山流，并受到南北向伸展的影响。两种不同类型的火山可以被描述为：锥形的，平顶的和粗糙的，细长的，与狭窄的，E - W走向的火山脊相关，其中一些在EM12图像上显示出强烈的后向散射。根据海山链的形态和熔岩样品的年龄，我们推断火山脊的岩浆来源与通过地幔三维对流环流向脊轴的馈送有关。我们认为，大约5 Ma以来相对板块运动的变化可能导致了脊轴下地幔上升流环流的偏移，从而使太平洋脊翼下异常热的地幔上升。这种运动变化也可能是梅纳德地块南部年轻岩石圈构造变形的原因。
Non–hot spot, intraplate volcanism is a common feature near the East Pacific Rise or Pacific‐Antarctic ridge. Volcanic ridges and seamount chains, tens to hundreds of kilometers long, are asymmetrically distributed about the ridge axis, with most volcanic features occurring on the Pacific plate. Their origins remain controversial. We have analyzed off‐axis volcanic ridges near the Pacific‐Antarctic ridge from bathymetry, backscatter, gravity, and geochemistry data of the Pacantarctic 2 cruise. K/Ar dating of samples dredged on these structures reveals a contrast of up to 3 Ma between the volcanoes and the underlying crust. The volcanic activity, as suggested by the strong backscatter in sonar images, appears to be limited to areas of seafloor younger than about 3 Ma. All surveyed ridges north of the Menard transform fault (TF) show recent activity close to the ridge axis and are not affected by faults. The off‐axis volcanic ridges south of the Menard TF show recent volcanic flows in their center and are affected by N‐S extension. Two different types of volcanoes can be characterized: conical, flat‐topped ones and rough, elongated ones associated with narrow, E‐W trending volcanic ridges, some of them showing strong backscattering on the EM12 imagery. From the morphology of the seamount chains and the ages of the lava samples, we infer that the magma source for the volcanic ridges is related to the feeding of the ridge axis through three‐dimensional mantle convective circulation. We suggest that a change in the relative plate motion since about 5 Ma might have induced an offset of the mantle upwelling circulation under the ridge axis so that anomalously hot mantle rises under the Pacific ridge flank. The kinematic change is also likely responsible for the tectonic deformation in the young lithosphere south of Menard TF.