Geochemical evolution of arc magmatism during arc-continent collision, South Mayo, Ireland
Geochemical evolution of arc magmatism during arc-continent collision, South Mayo, Ireland
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DOI：
10.1130/0091-7613(2001)029
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发表时间：
2001-06
期刊：
影响因子：
5.8
通讯作者：
A. Draut;P. Clift
中科院分区：
文献类型：
--
作者：
A. Draut;P. Clift
位于爱尔兰西部喀里多尼德山脉的纳福伊湖弧线在奥陶纪早期与劳伦蒂亚地区相撞。这一事件记录在南马约海槽的地层学中，南马约海槽是该系统保存下来的弧前盆地。位于最古老的纳福伊湖群底部的熔岩显示了洋内弧的组成。Lough Nafooey群(约495-481 Ma)END(T)降低，轻稀土元素(REE)变得更富，反映了早期与劳伦西亚的碰撞。随后的图尔马卡迪群(约481-470 Ma)为流纹岩，轻稀土元素富集，具有强烈的负端(T)。这些岩石是在格兰宾造山运动期间喷发的。Rosroe组和Mweelrea组(470 Ma)的La/Sm和Nb/Zr值分布很广，反映了混合的地幔来源。这与邻近的康尼马拉变质地体的快速折返有关。弧的化学演化支持15m年内碰撞、造山和构造剥离的模式，并表明在弧-陆碰撞过程中可以发生比大陆地壳更丰富的岩浆成因，阐明了弧火山作用在大陆地壳形成中的潜在作用。
The Lough Nafooey arc, in the western Irish Caledonides, collided with Laurentia during the Early Ordovician. This event is recorded in the stratigraphy of the South Mayo trough, the preserved forearc basin of this system. Lavas at the base of the oldest Lough Nafooey Group show intraoceanic arc composition. eNd(t) decreases and light rare earth elements (REEs) become more enriched upsection in the Lough Nafooey Group (ca. 495‐ 481 Ma), reflecting early collision with Laurentia. The subsequent Tourmakeady Group (ca. 481‐470 Ma) is rhyolitic, light REE enriched, and has strongly negative eNd(t). These rocks were erupted during the Grampian orogeny. The Rosroe and Mweelrea Formations (,470 Ma) show wide scatter of La/Sm and Nb/Zr values, suggesting mixed mantle sources. This correlates with rapid exhumation of the adjacent Connemara metamorphic terrane. The chemical evolution of the arc supports models of collision, orogeny, and tectonic unroofing within ;15 m.y., and shows that genesis of magmas more enriched than continental crust can occur during arc-continent collision, clarifying the potential role of arc volcanism in continental crust formation.