...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Contributions to Mineralogy and Petrology >Behavior of MORB magmas at uppermost mantle beneath a fast-spreading axis: an example from Wadi Fizh of the northern Oman ophiolite
【24h】

Behavior of MORB magmas at uppermost mantle beneath a fast-spreading axis: an example from Wadi Fizh of the northern Oman ophiolite

机译：快轴下方最上地幔中MORB岩浆的行为：以阿曼北部蛇绿岩的Wadi Fizh为例

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Relationships of lithologies in uppermost mantle section of Oman ophiolite are highly complicated, harzburgites especially being closely associated with dunites, wehrlites, and gabbros. The petrology and geochemistry of the uppermost mantle section provide constrains on how MORB (mid-ocean ridge basalt) magmas migrate from the mantle to crust. We conducted detailed sampling at the uppermost mantle section of the northern Oman ophiolite (along Wadi Fizh), and it provides us with centimeter-scale lithological and mineral chemical heterogeneity. In particular, we found peculiar plagioclase-free harzburgites that have not been recorded from the current ocean floor, which contain high-Mg# [Mg/(Mg + Fe~(2+)) atomic ratio] clinopyroxenes that are almost in equilibrium (saturated) with MORB in terms of REE concentrations. They are from the uppermost mantle section underlying the wehrlite-dunite layer (=Moho transition zone;;MTZ) just beneath the layered gabbro. MORBs cannot be in equilibrium with harzburgites;;however, we call the peculiar harzburgites as "MORB-saturated harzburgite" for simplicity in this paper. The MORB-saturated harzburgites exhibit slightly enriched mineralogy (e.g., spinels with higher Ti and ferric iron, and clinopyroxenes with higher Ti and Na) and contain slightly but clearly more abundant modal clinopyroxene (up to 3.5 vol.%) than ordinary Oman depleted harzburgites (less than 1 vol.% clinopyroxene), which are similar to abyssal harzburgites. Gabbro-clino-pyroxenite bands, which were melt lenses beneath the ridge axis, are dominant around the MTZ. Detailed sampling around the gabbro-clinopyroxenite bands revealed that the MORB-saturated harzburgites appear around the bands. The interaction between a melt that was MORB-like and an ordinary harzburgite induced incongruent melting of orth-opyroxenes in harzburgites, and the melt chromatographi-cally intruded into the wall harzburgite and was modified to coexist with olivine and two pyroxenes at low melt/harz-burgite ratios. The modified melt left clinopyroxene (not clinopyroxene + plagioclase as in plagioclase-impregnated abyssal harzburgite) to form the MORB-saturated harzburgites in the vicinity (harzburgite) of the fracture, which are left as gabbro-clinopyroxenite bands. This local modification mimics the whole lithological and chemical variation of the MTZ and makes chemical variation of MORB suite at fast-spreading ridge.
机译：阿曼蛇绿岩最上层地幔部分的岩性关系非常复杂，尤其是哈兹伯格岩与榴辉岩，辉绿岩和辉长岩密切相关。地幔最上部的岩石学和地球化学为MORB（中洋脊玄武岩）岩浆如何从地幔迁移到地壳提供了约束。我们在阿曼北部蛇绿岩的最上层地幔段（沿瓦迪菲日）进行了详细采样，它为我们提供了厘米级的岩性和矿物化学非均质性。特别是，我们发现了从当前海床尚未记录到的无斜长石的特殊哈兹伯格岩，它们含有高Mg＃[Mg /（Mg + Fe〜（2+））原子比]的斜茂铁几乎处于平衡状态（就稀土元素浓度而言，用MORB饱和。它们来自位于层状辉长岩下方的辉绿岩-榴layer石层（= Moho过渡带; MTZ）的最上层地幔部分。 MORB不能与Harzburgite保持平衡;但是，为简单起见，我们将特殊的Harzburgite称为“ MORB饱和Harzburgite”。 MORB饱和的哈茨伯格岩具有稍微富集的矿物学特征（例如，具有更高的Ti和三价铁的尖晶石，以及具有更高的Ti和Na的斜向辉石），并且比普通的阿曼贫化的哈茨伯格岩含有稍多但明显更丰富的模态斜辉石（高达3.5％（体积））。 （少于1 vol。％的clinopyroxene），与深渊哈兹伯格人相似。 Gabbro-斜辉石-辉石岩带是山脊轴下方的熔融透镜，在MTZ附近占主导地位。在辉长岩-斜辉石岩带周围进行的详细采样显示，MORB饱和的哈兹伯格岩出现在该带附近。类似于MORB的熔体与普通的Harzburgite之间的相互作用导致Harzburgite中邻位茂铁的不完全熔化，并且色谱色谱法侵入到Harzburgite壁中，并进行了改性，使其在低熔体/ Harz下与橄榄石和两种辉石共存。 -伯氏体比率。改性的熔融物留下斜长石（斜长石浸渍的深渊哈茨石中不像斜长石+斜长石）在裂缝附近（harzburgite）形成MORB饱和的长石辉石，这些辉长岩保留为辉长岩-斜辉石带。这种局部修饰模仿了MTZ的整个岩性和化学变化，并使MORB套件在快速扩散的脊上发生了化学变化。

著录项

相似文献

  • 外文文献
  • 中文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号