Forearc ages reveal extensive short-lived and rapid seafloor spreading following subduction initiation
Forearc ages reveal extensive short-lived and rapid seafloor spreading following subduction initiation
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DOI：
10.1016/j.epsl.2018.11.020
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发表时间：
2019-01
影响因子：
5.3
通讯作者：
M. Reagan;D. Heaton;M. Schmitz;J. Pearce;J. Shervais;A. Koppers
中科院分区：
文献类型：
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作者：
M. Reagan;D. Heaton;M. Schmitz;J. Pearce;J. Shervais;A. Koppers
伊豆-波宁-马里亚纳（IBM）前弧记录了始新世早期一次广泛而短暂的俯冲起始事件。我们提出了新的高精度年龄，以确定沿IBM汇聚边缘俯冲开始后洋壳生产的速率和长度尺度。我们还探讨了这些年龄对俯冲开始的潜在原因及其远场影响的影响。新海6500潜水采集的辉长岩中锆石的结晶年龄（±2σ）分别为51.94±0.13 Ma和51.81±0.03 Ma，与整个IBM体系在俯冲开始后几乎同步的海底扩张相一致。IODP 352考察期间，前弧玄武岩（51.34±0.78 Ma）和博宁辉长岩（51.27±0.09 Ma ~ 50.33±0.55 Ma）的氩/氩年龄进一步表明，前弧外由海洋岩石圈组成，由海底扩张在0.6-2 Myr的极短时间内以c. 70 mm/yr的全速率形成。这一时期与一些年代确定的蛇绿岩相一致。因此，近海沟海底扩张形成玄武岩-博尼米岩岩石圈是俯冲开始后一个广泛、快速、短暂的过程。
The Izu–Bonin–Mariana (IBM) forearc contains a record of a widespread and short-lived subduction initiation event in the early Eocene. We present new high-precision ages to determine the rates and length scales of ocean crust production following subduction initiation along the IBM convergent margin. We also explore the implications of these ages for potential causes of subduction initiation and its far-field effects. Zircons extracted from gabbros collected by Shinkai 6500 diving within the ophiolitic sequence exposed in the outer Bonin and Mariana forearcs give crystallization ages (±2σ) of 51.94 ± 0.13 Ma and 51.81 ± 0.03 Ma, respectively, consistent with a near-synchronous seafloor spreading after initiation of subduction along the entire length of the IBM system.40Ar/39Ar ages of forearc basalts (51.34 ± 0.78 Ma) and boninites (51.27 ± 0.09 Ma to 50.33 ± 0.55 Ma) cored upslope of the Bonin sample gabbro during IODP Expedition 352 further reveal that the outer forearc comprises oceanic lithosphere with MORB to boninite compositions created by seafloor spreading during a remarkably short time period of 0.6–2 Myr at a full-rate of c. 70 mm/yr. This time period is consistent with those of some well-dated ophiolites. Thus, near-trench seafloor spreading to form basalt then boninite lithosphere is an extensive, rapid, but short-lived process after subduction initiation.