Comparative study of oceanic plate and ophiolite based on accurate analyses of crustal and mantle material

主要研究结果如下：对采自阿曼北方蛇绿岩大面积区域的地幔方辉橄榄岩进行了系统的矿物学和岩石学分析，结果表明，在地幔剖面中存在一个高度亏损带。贫化带由具有高Cr#（Cr/（Cr+Al））的Cr尖晶石的出现来定义，并且沿着French小组描述的NW-SE走向的剪切带追踪。在大洋逆冲运动过程中，由于下伏基底排出的流体侵入，造成地幔部分重熔，形成这种亏损带。我们研究了幔壳过渡带的区域变化。7条路线的岩性柱分布在一个分段构造的不同位置，表明幔壳过渡带随分段构造的系统变化如下。过渡区厚度向管段中心逐渐增厚，在管段边缘逐渐变薄， ...更多信息 n.然而，从Wadi Fizh的北方贡分支发现异常厚的过渡带，位于该段的最边缘。过渡带构造特征的系统性变化也很明显，即在段中心线理和叶理较发育，而在段边缘则不太发育。这些结果表明，地幔上涌和岩浆流动在板块中心更为活跃。并从分段结构的角度研究了不同地点喷出序列的岩性柱。系统的变化，就发生模式的喷出物被发现，如下：大量的流动是占主导地位的部分中心与许多数量的单位。而枕状熔岩主要分布在岩段边缘，其厚度远大于岩段中心。因此，无论是地壳最上层的喷出物，还是地壳深部的喷出物，都受分段构造的控制。少

The results obtained from this research project are summarized as follows.Systematic mineral and bulk rock analyses for mantle harzburgites sampled from extensive area of the northern Oman ophiolite indicate that a highly depleted zone is present within the mantle section. The depleted zone is defined by the appearance of Cr-spinels with high Cr# (Cr/(Cr+Al), and traced along the shear zone trending NW-SE described by French group. Remelting of mantle sections caused by invasion of fluids expelled from the underling basement during oceanic thrusting movement would bring a such depleted zone.We have examined a regional variation of the mantle-crust transition zone. Lithologic column obtained from7 routes, located at different locations in a segment architecture, indicate a systematic variation of the mantle-crust transition zone depending on the segment structure, as follows. The thickness of the transition zone thickens toward the segment center, and become to thin at the segment margi … More n. However, abnormally thick transition zone was found from the northern tribute branch of Wadi Fizh, locating at the most margin of the segment. Systematic variations in structural features in the transition zone are also obvious, that is, intensive lineation and foliation are well observed at the segment center, while they are only poorly developed at the segment margin. These results suggest that mantle upwelling and magmatic flowage were more vigorous at the segment center. Also lithologic column for extrusive successions are studied at different localities in terms of segment structure. Systematic variations in respect to mode of occurrence of the extrusives were found, as follows: Massive flows are predominant at the segment center with numerous numbers of unit. Whereas, pillow lavas are predominant at the segment margin and are characterized by much thicker unit than the segment center. Thus, both extrusives in the uppermost level, and deeper section of the crust, were controlled by segmentation structure. Less