| 摘要: |
| 1994年4－11月，国家海洋局组织和实施了DY85－4航次中国开辟区（太平洋CC区）多金属结核（下简称结核）勘探，海上勘查历时225d，勘查面积达65×103km2，其中，用重力、磁力和单道地震等方法对测区进行了地球物理调查。结果表明，火山和浅层侵入体是提供给核生成的重要物质来源。区域性的沉积间断是造成结核丰度偏高的重要因素。断块活动强烈的地区，断裂活动有利于金属元素在海底的富集。不同时代形成的海底，地幔原岩在成分上的差异或在洋壳形成过程中构造活动的差异，对结核的形成有着一定的控制因素。而上述地质构造活动，在地球物理特征上都有着明显的反映。由此可见，地球物理特征与结核的形成和富集规律有着明显的相关关系。 |
| 关键词: 克拉里昂-克里帕顿断裂带 火山活动 断块活动 多金属结核成矿条件 |
| DOI： |
| 分类号: |
| 基金项目:“九五”中国大洋协会“资源评价与地质研究”项目，DY95-02-04号 |
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| A STUDY ON THE TECTONIC FEATURE AND POLYNETAL NODULE MINERALIZATION CONDITION IN THE CC REGION OF THE PACIFIC OCEAN |
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WANG Shu-gong, LIU Zhong-Chen, LIU Bao-hua, WU Jin-long
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First INstitute of Oceanography, State Oceanic Administration, Qingdao, 266003
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| Abstract: |
| According to the Eighth Five-year plan of Oceanic Polymetal Nodule Research and Development of COMRA, the State Oceanic Administration (SOA) organized and carried out a polymetal nodule exploration cruise DY85-4 in the CC region of the Pacific Ocean with a total area of 65×103km2 from April to November, 1994, with a period of 225d.
During the cruise the geophysical investigations including gravity, magnetic and single-channel seismic survey were conducted. A total single-channel seismic profile of 1533.7km with a high resolution and gravity and magnetic profile of 2227km with a high accuracy were obtained. Post-processing and stratigraphical analyses for the seismic profiles have been undertaken. The Moho depth has been calculated by using sinx/x method based on the surveyed Bouguer anomaly. A theoretical magnetic anomaly profile has been calculated using the two-dimensional plate formula and compared with the measured magnetic profiles, from which the age of ocean bottom was determined.
The results show that technically the volcanic activities dominate the west area and faulting block activities play a leading role in the east area. The difference in the tectonic background in the two areas causes the difference in the formation, distribution, abundance and types of the polymetal nodule.
The volcanic and shallow intrusive bodies provide the material source for the nodule. Especially the melt rock erupted up to the ocean bottom supplies the useful metal to water body (including bottom water and interval water) by the bottom weathering, being advantageous to the formation and concentration of the nodule.
Regional sediment discontinuation is caused mainly by the erosion due to bottom currents. This eroding action is very strong, which leads to the sediment discontinuation or low sedimental rate since the Miocene over the west area. It may be one of the reasons for the relatively high nodule abundance is relatively high in the area.
In the east area the faulting block activities are quite strong. From the analysis on the surveyed geophysical data, the faults may have formed channels for the water circulation, which is also advantageous to the concentration of the metal composition on the ocean bottom. However, since there exist scouring and reaccumulation on the slope zone between the lifting and descending walls of the fault, the regularity of the nodule concentration and distribution near the faults needs a further study. For the ocean bottoms formed in the different geological periods, the difference in the mantle original rock composition or in the tectonic activity during ocean crust formation could control the nodule forming to some extent.
In the west area the volcanic activities are strong, especially in the middle-south part where three sea mountain chains with a near east-west trend exist. The surveyed data show that the shallow intrusive igneous bodies develop widely. Based on the strong bottom current data three channels have been determined, which made the Miocene sediments discontinue. All these factors are important for the higher abundance and uniform distribution of the nodule.
The mineralization condition in the east area is similar to that in the west area. The intrusive volcanic activities in the east area are weak and do not develop in most areas except the middle and south-west parts. The sediment layers in the east area can generally reach a total thickness of 200–300ms. However, in the west area many shallow intrusive igneous bodies cut off layer III, II and I, which make sediment layers thin. In addition, the bottom water current activities in the east area are not as strong as that in the west area. The tectonic background mentioned above has caused the lower abundance and uniform distribution of the nodule. |
| Key words: Clarion-Clipperton fracture zones, Volcanic activities, Faulting block activities, Polymetal nodule mineralization condition |
