Geophysical and Petrological Study of the Northern Chile Ridge: Investigating Thermal Effects of Transform Offsets onRidge Axis Morphology, Crustal Thickness and Magmatism

OCE 96-18401（夏威夷大学：J. Karsten/F.）。这个联合项目将对智利北部脊和瓦尔迪维亚断裂带的变形扩展中心进行详细的地球物理和地球化学研究。一个为期40天的野外项目将使用SeaBeam 2000、磁学和重力来绘制轴向区域的详细地形图，直至布鲁内斯-松山磁极反转边界。新火山带将在约125个地点通过疏浚和蜡取芯进行采样；利用电子探针、ICP-MS、DCP、质谱等方法分析主元素、微量元素和Pb-Nd-Sr同位素特征。结合智利北脊的数据集，将研究轴向深度、地壳结构和熔岩组成与大偏移转换断层相关的热效应的关系。Valdivia f.z数据集将用于进一步研究先前在智利南脊研究中发现的东南太平洋异常地球化学特征的范围和变异性（即DUPAL同位素特征和具有俯冲带微量元素特征的MORB），并将正在进行的太平洋中洋脊玄武岩化学与轴向深度之间关系的研究扩展到更深的脊段。

Abstract OCE 96-18401 (University of Hawaii: J. Karsten/F. Martinez) OCE 96-18736 (Duke University: E. Klein) This combined program will conduct a detailed geophysical and geochemical study of the Northern Chile Ridge and Valdivia Fracture Zone intra-transform spreading centers. A 40-day field program will use SeaBeam 2000, magnetics, and gravity to map the detailed geomorphology of the axial region out to the Brunhes-Matuyama magnetic reversal boundary. The neo-volcanic zone will be sampled at ~125 sites by dredging and wax coring; lavas recovered will be analyzed by electron microprobe, ICP-MS, DCP, and mass spectrometry for major element, trace element, and Pb-Nd-Sr isotopic characteristics. The combined data set for the Northern Chile Ridge will be used to investigate the relationship of axial depth, crustal structure and lava composition with thermal effects associated with large offset transform faults. The Valdivia F.Z. data set will be used to further investigate the extent and variability of anomalous geochemical features of the Southeast Pacific discovered in previous studies of the Southern Chile Ridge (i.e., DUPAL isotopic signatures and MORB with subduction zone trace element characteristics) and to extend on-going studies of relationships between Pacific mid-ocean ridge basalt chemistry and axial depth to deeper ridge segments.