Subsidence and growth of Pacific Cretaceous plateaus
Subsidence and growth of Pacific Cretaceous plateaus
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DOI：
10.1016/s0012-821x(98)00139-3
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发表时间：
1998-09
影响因子：
5.3
通讯作者：
G. Ito;P. Clift
中科院分区：
文献类型：
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作者：
G. Ito;P. Clift
Ontong Java，Manihiki和Shatsky海洋高原是地球上最大的火成岩省之一，通常被认为是在启动地幔柱的巨大头部浮出水面时迅速爆发的。我们调查了这一假设，通过使用深海钻探计划（DSDP）和大洋钻探计划（ODP）的岩心沉积物的描述，以限制高原沉降的历史，反映地幔热和地壳增生过程。我们发现，总的高原沉降与正常海底的预期相当，但低于热点影响的岩石圈热模型的预测。如果地壳侵位是迅速的，那么古水深的不确定性允许预测的异常沉降，只有适度的温度异常和体积，相当于现代热点的来源，如夏威夷和冰岛。然而，在高温和高体积的羽流头上的快速就位很难与沉降重建相协调。另一种可能性是，在高温、高体积的地幔柱源上调和低沉降，在这种情况下，高原沉降是（1）由于地幔柱源冷却而引起的沉降和（2）由于岩浆底侵形式的地壳长时间生长而引起的隆起的叠加。这种长期的地壳生长和隆起的情况可以解释低，从而在羽状流的启动，在Ontong Java（90 Ma）和Manihiki（170 Ma），高地震速度下地壳的大部分，以及广泛的正断层观察到整个和沿着边缘的三个高原发现的晚期喷发海底浮雕。这种晚期底侵作用可能是连续发生的，也可能是在超过1.3亿年的时间里以不连续的阶段发生的。这意味着较低的岩浆流量比以前估计。
The Ontong Java, Manihiki, and Shatsky oceanic plateaus are among the Earth's largest igneous provinces and are commonly believed to have erupted rapidly during the surfacing of giant heads of initiating mantle plumes. We investigate this hypothesis by using sediment descriptions of Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill cores to constrain plateau subsidence histories which reflect mantle thermal and crustal accretionary processes. We find that total plateau subsidence is comparable to that expected of normal seafloor but less than predictions of thermal models of hotspot-affected lithosphere. If crustal emplacement was rapid, then uncertainties in paleo-water depths allow for the anomalous subsidence predicted for plumes with only moderate temperature anomalies and volumes, comparable to the sources of modern-day hotspots such as Hawaii and Iceland. Rapid emplacement over a plume head of high temperature and volume, however, is difficult to reconcile with the subsidence reconstructions. An alternative possibility that reconciles low subsidence over a high-temperature, high-volume plume source is a scenario in which plateau subsidence is the superposition of (1) subsidence due to the cooling of the plume source, and (2) uplift due to prolonged crustal growth in the form of magmatic underplating. This prolonged crustal growth and uplift scenario may explain the low and thus submarine relief during plume initiation, the late stage eruptions found on Ontong Java (90 Ma) and Manihiki (∼70 Ma), a large portion of the high-seismic-velocity lower crust, and the widespread normal faults observed throughout and along the margins of the three plateaus. Such late stage underplating may have occurred continuously or in discrete stages over ∼30 m.y. and implies lower magmatic fluxes than previously estimated.