Reply to 'Unclear causes for subduction'-猫眼课题宝

DOI：

10.1038/ngeo2704

发表时间：

2016-05

期刊：

Nature Geoscience

影响因子：

18.3

通讯作者：

中科院分区：

地球科学1区

文献类型：

作者：

R. Arculus;O. Ishizuka;K. Bogus;M. Gurnis;R. Hickey‐Vargas;M. Aljahdali;A. N. Bandini-Maeder;A. Barth;P. Brandl;L. Drab;R. M. Guerra;M. Hamada;F. Jiang;K. Kanayama;S. Kender;Y. Kusano;He Li;L. Loudin;M. Maffione;K. Marsaglia;A. McCarthy;S. Meffre;A. Morris;M. Neuhaus;I. Savov;C. Sena;F. Tepley;C. Land;G. Yogodzinski;Zhaohui Zhang

Encarnación表明，U1438点岩心资料中没有俯冲前起始基底，这使我们对伊豆-博宁-马里亚纳系统自发俯冲起始的结论存在不确定性。然而，没有证据表明伊豆-博宁-马里亚纳体系在裂谷之前的最早产物在该地区的任何地方都保存了隆起。三个次平行的脊——从北到南，奄美高原，大东和冲基大东脊（图1来自参考文献1）——包括在伊豆-波宁-马里亚纳系统之前形成的中生代-第三纪弧的岩浆产物。这些隆起与伊豆-波宁-马里亚纳体系中最早的层状火山链——九州-帕劳脊呈东西垂直走向。如果挤压先于开始，正如强迫俯冲模型2所暗示的那样，我们预计老弧脊的隆起，向西减弱，沉积物从隆起的地区流入邻近的盆地。这些预测的影响都没有被观察到。Amami高原、Daito和Oki-Daito山脊并非向东变浅，而是向西变浅，这可能是由于伊豆-小原-马里亚纳系统形成后东部地区的下沉所致。地壳厚度沿脊向变化迅速，没有东西挤压增厚3,4。此外，南大东盆地下始新世沉积序列早于伊豆-波宁-马里亚纳造山期，为无碎屑泥岩5。与这些沉积物相穿插的玄武岩断层为碱性板内型，缺乏俯冲带输入，符合裂谷环境6。缺乏证据表明伊祖-波宁-马里亚纳盆地前的基底受到挤压，再加上我们所记录的最早的弧产物伴随的裂谷和海底扩张，这与自然起裂模型是一致的。强迫和自发俯冲开始模型2都过于简化了。这个过程很可能是强三维的，很可能是从现存的俯冲系统沿走向传播的。对于伊豆-波宁-马里亚纳系统，随着原菲律宾海板块的顺时针旋转，从原菲律宾海板块南边界的俯冲带向北传播是可能的。古老、致密的太平洋板块岩石圈与相对浮力较大的中生代至下第三纪弧形岩石圈的并置，可能对一个新的俯冲带的自发成核至关重要

Encarnación suggest that the absence of pre-subduction inception basement in the drill core data taken from site U1438 raises ambiguity in our conclusion of spontaneous subduction initiation in the Izu–Bonin–Mariana system1. However, there is no evidence for uplift in the earliest products of the Izu–Bonin–Mariana system preceding rifting preserved anywhere in the region. Three sub-parallel ridges—from north to south, the Amami plateau, Daito and Oki-Daito ridges (Fig. 1 from ref. 1)—comprise magmatic products of Mesozoic–Tertiary arcs formed prior to the Izu–Bonin–Mariana system. These ridges generally strike east–west orthogonally to the Kyushu–Palau ridge—the earliest stratovolcano chain of the Izu–Bonin–Mariana system. If compression preceded inception, as implied by the forced subduction model2, we anticipate uplift of the old arc ridges, diminishing in effect westwards, and sediment shedding from uplifted regions into adjacent basins. None of these predicted effects are observed. The Amami plateau, Daito and Oki-Daito ridges do not shallow eastwards, rather they shallow westwards3, possibly due to subsidence of the eastern sectors following inception of the Izu–Bonin–Mariana system4. Crustal thicknesses change rapidly across-strike of the ridges, showing no east–west compressional thickening3, 4. Furthermore, Lower Eocene sedimentary sequences in the Minami Daito basin, which predate Izu–Bonin–Mariana inception, are clast-free mudstone5. Basalt sills intercalated with these sediments are alkaline intraplate types lacking subduction zone input, consistent with a rifting environment6. This lack of evidence for compression of pre-Izu–Bonin–Mariana basement, coupled with the rifting and seafloor spreading accompanying the earliest arc products that we document1 is consistent with a spontaneous initiation model. Both forced and spontaneous subduction inception models2 are oversimplified. The process is likely to be strongly threedimensional and probably propagates along-strike from an extant subduction system7. For the Izu–Bonin–Mariana system, northward propagation from a subduction zone on the southern boundary of the proto-Philippine Sea plate as the latter rotated clockwise is possible1. Juxtaposition of old, dense Pacific plate lithosphere against the relatively buoyant lithosphere of the Mesozoic to Lower Tertiary arcs could have been critical for the spontaneous nucleation of a new subduction zone8.❐

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