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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Structure and evolution of the Afanasy Nikitin seamount, buried hills and 85°E Ridge in the northeastern Indian Ocean
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Structure and evolution of the Afanasy Nikitin seamount, buried hills and 85°E Ridge in the northeastern Indian Ocean

机译：印度洋东北部Afanasy Nikitin海山，潜山和85°E脊的结构和演化

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摘要

Geophysical data of the Afanasy Nikitin seamount (ANS), partly buried hills and 85°E Ridge in the northeastern Indian Ocean were studied together with published seismic refraction results to understand genesis and evolution of the structures. The ANS joins the 85°E Ridge through isolated buried hills and intervening subsurface structures and together they form a linear ridge system. The gravity signature of the ridge system changes from negative to positive towards south of 5°N, which seems to coincide with termination/thinning of pre-collision continental sediments in the Bay of Bengal. Thick pile of Bengal Fan sediments had great impact on underneath pre-collision sediments as well as on basement rocks; the process resulted in attaining higher velocities, up to 6.6 and 7.1 km/s, respectively. Gravity model studies suggest that structures of the ridge system are compensated in different modes. The ANS is underlain by an 8 km thick, deep crustal body of magmatic rocks, while beneath other structures oceanic crust is down-flexed up to 2.5 km. The presence of metasediments, more dense than volcanic rocks, and flexure of the lithosphere would explain the negative gravity anomaly over the 85°E Ridge, whereas lack of metasediments and magmatic rocks at depth would explain the compensated positive anomaly over the ANS. The width of the 85°E Ridge, the wavelength (～190 km) and amplitude (～2.5 km) of the flexed oceanic crust and the intersection of the ridge with the Mesozoic fracture zones suggest that the ridge was formed in intraplate position when the lithosphere underneath was approximately 35 Myr old. Initial emplacement of the ANS was coeval with the formation of oceanic lithosphere at 80-73 Ma. The hotspot forming the 85°E Ridge had reactivated the ANS during the Paleocene and brought it to the sea surface. Then it underwent erosion and subsidence processes. The deformation activity had converged the north and south parts of the ANS at late Miocene and again at late Pleistocene and northward buried hills at early Pliocene.
机译：研究了印度洋东北部的Afanasy Nikitin海山（ANS），部分埋藏的山丘和85°E脊的地球物理数据，以及已发表的地震折射结果，以了解结构的成因和演化。 ANS通过孤立的掩埋山丘和中间的地下结构加入85°E脊，它们一起形成线性脊系统。脊系统的重力特征从负向正向在5°N以南变化，这似乎与孟加拉湾碰撞前大陆沉积的终止/变薄一致。孟加拉扇沉积物的厚桩对碰撞前的沉积物以及基底岩石有很大的影响。该过程导致了更高的速度，分别达到了6.6 km / s和7.1 km / s。重力模型研究表明，脊系统的结构以不同的方式得到补偿。 ANS位于8公里厚的深厚岩浆岩地壳之下，而在其他结构下方，洋壳向下弯曲至2.5公里。比火山岩更致密的沉积物的存在，以及岩石圈的挠曲可以解释85°E脊上的负重力异常，而缺乏深度的沉积物和岩浆岩则可以解释ANS上的补偿正异常。 85°E脊的宽度，弯曲的大洋壳的波长（〜190 km）和振幅（〜2.5 km）以及该脊与中生代断裂带的交点表明，该脊在板内位置形成。下方的岩石圈约35迈尔。 ANS的初始位置与80-73 Ma的大洋岩石圈形成相吻合。在古新世期间，形成85°E脊的热点重新激活了ANS，并将其带入海面。然后，它经历了侵蚀和沉降过程。变形活动使中新世晚期和后新世晚期以及上新世早期的北向掩埋山都集中在ANS的北部和南部。

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