EAST MARIANA BASIN THOLEIITES - CRETACEOUS INTRAPLATE BASALTS OF RIFT BASALTS RELATED TO THE ONTONG JAVA PLUME
EAST MARIANA BASIN THOLEIITES - CRETACEOUS INTRAPLATE BASALTS OF RIFT BASALTS RELATED TO THE ONTONG JAVA PLUME
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DOI：
10.1016/0012-821x(94)90263-1
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发表时间：
1994-05-01
影响因子：
5.3
通讯作者：
CARLSON, RW
中科院分区：
文献类型：
--
作者：
CASTILLO, PR;PRINGLE, MS;CARLSON, RW
对海底磁异常模式的研究表明，在包括东马里亚纳、瑙鲁和皮加费塔盆地在内的西太平洋大片地区存在侏罗纪洋壳。深海钻探计划（DSDP）和大洋钻探计划（ODP）对这一地区的火成岩地壳进行取样，可以直接评估该地壳的年龄和岩石成因。ODP第129航次在东马里亚纳盆地中部钻探了一个51米长的玄武岩枕和块状流序列。本文测定的两个129柱玄武岩的~（40）Ar/~（39）Ar年龄平均为114.6 ± 3.2 Ma。这一年龄与上覆沉积物的Albian-Late Aptian古生物年龄一致，但明显小于盆地磁异常模式预测的侏罗纪年龄。在成分上，东马里亚纳盆地玄武岩是均匀的低K拉斑玄武岩，与中度不相容的玄武岩相比，它们在高度不相容的元素中耗尽，这是典型的在热点附近爆发的洋中脊玄武岩（MORB）。拉斑玄武岩的Sr、Nd、Pb同位素组成（Sr-87/Sr-86（init）= 0.70360-0.70374; Nd-143/Nd-144（init）= 0.512769-0.512790; Pb-206/Pb-204（meas）= 18.355-18.386）也与一些印度洋脊MORB重叠，尽管它们与在Pigafetta盆地钻探的侏罗纪玄武岩的同位素组成不同，Pigafetta盆地是最古老的太平洋MORB。东马里亚纳盆地拉斑玄武岩的同位素组成也类似于板内玄武岩，特别是从附近的Ontong Java和Manihiki高原的玄武岩的同位素签名。东马里亚纳盆地拉斑玄武岩还与瑙鲁盆地DSDP 462号站点钻探的海洋基底具有许多岩石学和同位素特征。此外，新的110.8 +/- 1.0 Ma 40 Ar/39 Ar年龄的两个流量从底部的站点462在瑙鲁盆地是无法区分的年龄的东马里亚纳盆地流。因此，虽然磁异常模式预测，在瑙鲁和东马里亚纳盆地的火成岩基底是侏罗纪的年龄，地球化学和年代学的结果在这里讨论表明，在侏罗纪地壳内的白垩纪裂谷事件的基础上形成的。这一岩浆和构造事件是由广泛的火山活动造成的，火山活动是西太平洋大型海洋高原的成因，海底磁异常模式的研究表明，在包括东马里亚纳、瑙鲁和皮加费塔盆地在内的西太平洋大片地区存在侏罗纪海洋地壳。深海钻探计划（DSDP）和大洋钻探计划（ODP）对这一地区的火成岩地壳进行取样，可以直接评估该地壳的年龄和岩石成因。ODP第129航次在东马里亚纳盆地中部钻探了一个51米长的玄武岩枕和块状流序列。本文测定的两个129柱玄武岩的~（40）Ar/~（39）Ar年龄平均为114.6 ± 3.2 Ma。这一年龄与上覆沉积物的Albian-Late Aptian古生物年龄一致，但明显小于盆地磁异常模式预测的侏罗纪年龄。在成分上，东马里亚纳盆地玄武岩是均匀的低K拉斑玄武岩，与中度不相容的玄武岩相比，它们在高度不相容的元素中耗尽，这是典型的在热点附近爆发的洋中脊玄武岩（MORB）。拉斑玄武岩的Sr、Nd、Pb同位素组成（Sr-87/Sr-86（init）= 0.70360-0.70374; Nd-143/Nd-144（init）= 0.512769-0.512790; Pb-206/Pb-204（meas）= 18.355-18.386）也与一些印度洋脊MORB重叠，尽管它们与在Pigafetta盆地钻探的侏罗纪玄武岩的同位素组成不同，Pigafetta盆地是最古老的太平洋MORB。东马里亚纳盆地拉斑玄武岩的同位素组成也类似于板内玄武岩，特别是从附近的Ontong Java和Manihiki高原的玄武岩的同位素签名。东马里亚纳盆地拉斑玄武岩还与瑙鲁盆地DSDP 462号站点钻探的海洋基底具有许多岩石学和同位素特征。此外，新的110.8 +/- 1.0 Ma 40 Ar/39 Ar年龄的两个流量从底部的站点462在瑙鲁盆地是无法区分的年龄的东马里亚纳盆地流。因此，虽然磁异常模式预测，在瑙鲁和东马里亚纳盆地的火成岩基底是侏罗纪的年龄，地球化学和年代学的结果在这里讨论表明，在侏罗纪地壳内的白垩纪裂谷事件的基础上形成的。这一岩浆和构造事件是由广泛的火山活动造成的，火山活动是西太平洋大海洋高原的成因。
Studies of seafloor magnetic anomaly patterns suggest the presence of Jurassic oceanic crust in a large area in the western Pacific that includes the East Mariana, Nauru and Pigafetta Basins. Sampling of the igneous crust in this area by the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Program (ODP) allows direct evaluation of the age and petrogenesis of this crust. ODP Leg 129 drilled a 51 m sequence of basalt pillows and massive flows in the central East Mariana Basin. 40Ar/39Ar ages determined in this study for two Leg 129 basalts average 114.6 +/- 3.2 Ma. This age is in agreement with the Albian-late Aptian paleontologic age of the overlying sediments, but is distinctively younger than the Jurassic age predicted by magnetic anomaly patterns in the basin. Compositionally, the East Mariana Basin basalts are uniformly low-K tholeiites that are depleted in highly incompatible elements compared to moderately incompatible ones, which is typical of mid-ocean ridge basalts (MORB) erupted near hotspots. The Sr, Nd and Pb isotopic compositions of the tholeiites (Sr-87/Sr-86(init) = 0.70360-0.70374; Nd-143/Nd-144(init) = 0.512769-0.512790; Pb-206/Pb-204(meas) = 18.355-18.386) also overlap with some Indian Ocean Ridge MORB, although they are distinct from the isotopic compositions of Jurassic basalts drilled in the Pigafetta Basin, the oldest Pacific MORB. The isotopic compositions of the East Mariana Basin tholeiites are also similar to those of intraplate basalts, and in particular, to the isotopic signature of basalts from the nearby Ontong Java and Manihiki Plateaus. The East Mariana Basin tholeiites also share many petrologic and isotopic characteristics with the oceanic basement drilled in the Nauru Basin at DSDP Site 462. In addition, the new 110.8 +/- 1.0 Ma 40Ar/39Ar age for two flows from the bottom of Site 462 in the Nauru Basin is indistinguishable from the age of the East Mariana Basin flows. Thus, while magnetic anomaly patterns predict that the igneous basement in the Nauru and East Mariana Basins is Jurassic in age, the geochemical and chronological results discussed here suggest that the basement formed during a Cretaceous rifting event within the Jurassic crust. This magmatic and tectonic event was created by the widespread volcanism responsible for the genesis of the large oceanic plateaus of the western Pacific.Studies of seafloor magnetic anomaly patterns suggest the presence of Jurassic oceanic crust in a large area in the western Pacific that includes the East Mariana, Nauru and Pigafetta Basins. Sampling of the igneous crust in this area by the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Program (ODP) allows direct evaluation of the age and petrogenesis of this crust. ODP Leg 129 drilled a 51 m sequence of basalt pillows and massive flows in the central East Mariana Basin. 40Ar/39Ar ages determined in this study for two Leg 129 basalts average 114.6 +/- 3.2 Ma. This age is in agreement with the Albian-late Aptian paleontologic age of the overlying sediments, but is distinctively younger than the Jurassic age predicted by magnetic anomaly patterns in the basin. Compositionally, the East Mariana Basin basalts are uniformly low-K tholeiites that are depleted in highly incompatible elements compared to moderately incompatible ones, which is typical of mid-ocean ridge basalts (MORB) erupted near hotspots. The Sr, Nd and Pb isotopic compositions of the tholeiites (Sr-87/Sr-86(init) = 0.70360-0.70374; Nd-143/Nd-144(init) = 0.512769-0.512790; Pb-206/Pb-204(meas) = 18.355-18.386) also overlap with some Indian Ocean Ridge MORB, although they are distinct from the isotopic compositions of Jurassic basalts drilled in the Pigafetta Basin, the oldest Pacific MORB. The isotopic compositions of the East Mariana Basin tholeiites are also similar to those of intraplate basalts, and in particular, to the isotopic signature of basalts from the nearby Ontong Java and Manihiki Plateaus. The East Mariana Basin tholeiites also share many petrologic and isotopic characteristics with the oceanic basement drilled in the Nauru Basin at DSDP Site 462. In addition, the new 110.8 +/- 1.0 Ma 40Ar/39Ar age for two flows from the bottom of Site 462 in the Nauru Basin is indistinguishable from the age of the East Mariana Basin flows. Thus, while magnetic anomaly patterns predict that the igneous basement in the Nauru and East Mariana Basins is Jurassic in age, the geochemical and chronological results discussed here suggest that the basement formed during a Cretaceous rifting event within the Jurassic crust. This magmatic and tectonic event was created by the widespread volcanism responsible for the genesis of the large oceanic plateaus of the western Pacific.