Magnetic structure of an oceanic core complex at the southernmost Central Indian Ridge: Analysis of shipboard and deep‐sea three‐component magnetometer data
Magnetic structure of an oceanic core complex at the southernmost Central Indian Ridge: Analysis of shipboard and deep‐sea three‐component magnetometer data
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DOI：
10.1029/2008gc002267
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发表时间：
2009-06
期刊：
影响因子：
3.7
通讯作者：
Taichi Sato;K. Okino;H. Kumagai
中科院分区：
文献类型：
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作者：
Taichi Sato;K. Okino;H. Kumagai
根据最新收集的磁测和测深数据以及潜水资料，研究了位于中印度洋脊（CIR）最南端25°S附近的大洋核杂岩（OCC）的磁结构。OCC位于CIR西侧的离轴位置，其特征在于具有流线平行波纹的典型巨棒形态。OCC的大小与沿着大西洋中脊（MAR）发现的OCC相似，但CIR OCC形成于估计的0.8 Ma，略短于沿着MAR形成OCC的平均时间。CIR OCC上的磁化强度与相同年龄的相邻海底相比相当弱。大多数辉长岩是在潜水时从露头中发现的。断层岩也恢复了从波纹表面，这表明OCC表面代表了剥离断层的平面。虽然磁化强度相当低，但我们能够使用矢量磁分析确定OCC上和周围的Brunhes-Matuyama边界以及Jaramillo和Olduvai亚时。在OCC上方，无法从海面获取的磁力数据中识别的Jaramillo亚时线是使用附在潜水器上的磁力计的数据确定的。该亚时线的轨迹与OCC附近海底的观测结果一致。结合磁力测量和岩石取样的结果，我们想指出辉长岩构成OCC和保存海底扩张历史的可能性，尽管对低磁化有几种解释。
We investigated the magnetic structure of an oceanic core complex (OCC) at the southernmost Central Indian Ridge (CIR) near 25°S on the basis of newly collected magnetic and bathymetric data and submersible dives. The OCC is located off‐axis on the western flank of the CIR and is characterized by typical megamullion morphology with flow line–parallel corrugations. The OCC is similar in size to those found along the Mid‐Atlantic Ridge (MAR), but the CIR OCC formed in an estimated 0.8 Ma, which is slightly shorter than the average time for the formation of OCCs along the MAR. The magnetization intensity over the CIR OCC is quite weak compared to that over adjacent seafloor of the same age. Mostly gabbroic rocks were recovered from outcrops during submersible dives. Fault rocks were also recovered from the corrugated surface, suggesting that the OCC surface represents the plane of a detachment fault. Although the magnetization intensity is rather low, we were able to identify the Brunhes‐Matuyama boundary and the Jaramillo and Olduvai subchrons on and around the OCC using vector magnetic analysis. Over the OCC, the Jaramillo subchron, which cannot be recognized from magnetic data acquired at the sea surface, was identified using data from a magnetometer attached to a submersible. The locus of this subchron is consistent with that observed over the seafloor adjacent to the OCC. Combining the results of magnetic survey and rock sampling, we would like to point out the possibility that the gabbroic rocks constituted the OCC and preserved seafloor‐spreading history, although there are several interpretations of the low magnetization.