The ‘subduction initiation rule’: a key for linking ophiolites, intra-oceanic forearcs, and subduction initiation
The ‘subduction initiation rule’: a key for linking ophiolites, intra-oceanic forearcs, and subduction initiation
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DOI：
10.1007/s00410-011-0638-z
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发表时间：
2011-04
影响因子：
3.5
通讯作者：
S. Whattam;R. Stern
中科院分区：
文献类型：
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作者：
S. Whattam;R. Stern
我们建立了“俯冲起始规则”（SIR），该规则预测大部分蛇绿岩形成于俯冲起始（SI）期间，SIR蛇绿岩的诊断岩浆化学地层学进展是从HFSE亏损和LILE富集的成分较少到较多。这种化学地层学的演变反映了弧前岩石圈的形成是地幔熔融的结果，而地幔熔融又逐渐受到SI期间俯冲带富集作用的影响。Izu-Bonin-Mariana（IBM）前弧和大多数特提斯蛇绿岩的岩浆化学地层学进展是从MORB样到弧样（火山弧玄武岩或VAB ±玻尼岩或BON），因为SI进展直到建立成熟的俯冲带。类MORB熔岩是上涌软流圈减压熔融的产物，是SI的第一次岩浆表现。脱水的海洋地壳和沉积物上的下沉板流体的贡献是可以忽略不计的早期SI，但继续熔融的结果在耗尽，方辉橄榄岩残留物，是逐步交代的流体从下沉板;随后部分熔融的残留物产生“典型的”SSZ样熔岩在后期阶段的SI。如果S1被早期阻止，例如，作为碰撞的结果，可以预期“仅MORB”的蛇行。因此，MORB-和SSZ-唯一的蛇绿岩可能代表SI蛇绿岩光谱的端员。马里亚纳前弧的化学地层相似性与蛇绿岩，遵循SIR暗示，连接这样的蛇绿岩，海洋前弧，SI的模型是全球适用的。
We establish the ‘subduction initiation rule’ (SIR) which predicts that most ophiolites form during subduction initiation (SI) and that thediagnosticmagmatic chemostratigraphic progression for SIR ophiolites is from less to more HFSE-depleted and LILE-enriched compositions. This chemostratigraphic evolution reflects formation of what ultimately becomes forearc lithosphere as a result of mantle melting that is progressively influenced by subduction zone enrichment during SI. The magmatic chemostratigraphic progression for the Izu–Bonin–Mariana (IBM) forearc and most Tethyan ophiolites is specifically from MORB-like to arc-like (volcanic arc basalts or VAB ± boninites or BON) because SI progressed until establishment of a mature subduction zone. MORB-like lavas result from decompression melting of upwelling asthenosphere and are the first magmatic expression of SI. The contribution of fluids from dehydrating oceanic crust and sediments on the sinking slab is negligible in early SI, but continued melting results in a depleted, harzburgitic residue that is progressively metasomatized by fluids from the sinking slab; subsequent partial melting of this residue yields ‘typical’ SSZ-like lavas in the latter stages of SI. If SI is arrested early, e.g., as a result of collision, ‘MORB-only’ ophiolites might be expected. Consequently, MORB- and SSZ-only ophiolites may represent end-members of the SI ophiolite spectrum. The chemostratigraphic similarity of the Mariana forearc with that of ophiolites that follow the SIR intimates that a model linking such ophiolites, oceanic forearcs, and SI is globally applicable.