The case for persistent southwest-dipping Cretaceous convergence in the northeast Antilles: Geochemistry, melting models, and tectonic implications
The case for persistent southwest-dipping Cretaceous convergence in the northeast Antilles: Geochemistry, melting models, and tectonic implications
复制标题
安的列斯群岛东北部白垩纪持续向西南倾斜的汇聚情况：地球化学、融化模型和构造意义
DOI：
--
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
A. Dickin
中科院分区：
文献类型：
--
作者：
W. T. Jolly;E. Lidiak;A. Dickin
通过对波多黎各中部爆发的岛弧熔岩和侧翼海洋盆地中潜在的远洋沉积物储层之间的地球化学比较，提供了对大安的列斯群岛白垩纪俯冲作用极性的制约。早侏罗世至白垩纪中期（185- 65-Ma）的沉积物从开放的太平洋西南部的主要是远洋硅质岩，这是高度耐火和亏损的不相容元素。而中、晚白垩世（英语：Middle-Late Cretaceous）（约1000年）则是其中之一。112-65-Ma）的沉积物，从年轻的大西洋盆地东北部占主导地位的两个端员的混合物。其中包括（1）轻稀土元素（LREE）丰度高、高场强元素（HFSE）负异常、Zr/Sm低的生物成因粘土和碳酸盐岩;（2）上陆壳浊流碎屑，LREE高、HFSE异常较浅、Zr/Sm高。波多黎各弧玄武岩的成分与太平洋远洋燧石的结合不一致。相反，高铁岛弧拉斑玄武岩的模式特征是复制注册成立的低Zr/Sm生物沉积物成分的大西洋起源的4%，而低铁熔岩的模式需要，除了生物沉积物，引入高达2%的高Zr/ Sm地壳浊积岩成分。所有俯冲沉积物的大西洋起源表明整个白垩纪在东北安的列斯群岛的俯冲极性是持续西南倾斜。这一结论得到了来自波多黎各西南部的加勒比高原玄武岩（91 - 88 Ma）中存在起源于大西洋的低Zr/Sm超俯冲带成分的支持，这些玄武岩在弧发展的中期阶段在大安的列斯群岛广阔的弧后区域内喷发。
Constraints on the polarity of Cretaceous subduction in the Greater Antilles are provided through geochemical comparison between the erupted island arc lavas in central Puerto Rico and potential pelagic sediment reservoirs in the fl anking ocean basins. Early Jurassic to mid-Cretaceous (185- to 65-Ma) sediment from the open Pacifi c on the southwest is dominated by pelagic chert, which is highly refractory and depleted with respect to incompatible elements. In comparison, mid- to Late Cretaceous (ca. 112- to 65-Ma) sediment from the younger Atlantic basin on the northeast was dominated by mixtures of two end members. These include (1) biogenic clay and carbonates with elevated light rareearth element (LREE) abundances, negative MORB-normalized, high fi eld-strength element (HFSE) anomalies, and low Zr/Sm; and (2) turbiditic detritus of upper continental crust composition with high LREE, comparatively shallow HFSE anomalies, and high Zr/Sm. Compositions of Puerto Rican arc basalts are inconsistent with incorporation of Pacifi c pelagic chert. Instead, patterns characteristic of high-Fe island arc tholeiites are reproduced by incorporation of up to 4% of a low-Zr/Sm biogenic sediment component of Atlantic origin, whereas patterns of low-Fe lavas require, in addition to biogenic sediment, introduction of up to 2% of a high-Zr/ Sm crustal turbidite component. The Atlantic origin of all the subducted sediments indicates the polarity of subduction throughout the Cretaceous in the northeast Antilles was persistently southwest dipping. This conclusion is supported by the presence of a lowZr/Sm suprasubduction zone component of Atlantic origin in Caribbean plateau basalts (91‐88 Ma) from southwest Puerto Rico, which were erupted within the broad backarc region of the Greater Antilles during intermediate stages of arc development.