| 摘要: |
| 根据1986年10月—1987年5月第三次南极考察和首次环球科学考察所获的印度洋实测重力资料，对印度洋一些典型构造进行了分析研究。初步认为：无震海岭、海底高原和大洋中脊都有着复杂的壳-幔结构，其上都伴有一个布格异常的低值带，但引起这种布格异常低值带的原因却不尽相同。虽然上述3者都是大洋中的隆起地带，但前两者的地壳增厚，莫氏面下拱，软流圈变深，影响布格异常的主要因素是其下存在着一个较大的负山根。相反，在大洋中脊处，地壳变薄，莫氏面上拱，软流圈抬升，影响布格异常的主要因素是其下存在着一个高热、低速、低密度的异常地幔。构造运动剧烈的大洋中脊系，其强大的外力来源为地幔的热动力，它的地壳年龄虽新，但活动历史却很老，并已达到热动力平衡状态，而不是处于均衡状态。 |
| 关键词: 无震海岭 海底高原 大洋中脊 重力异常 深部构造 |
| DOI： |
| 分类号: |
| 基金项目:国家海洋局第一海洋研究所南极考察课题，102101号 |
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| A PRELIMINARY STUDY ON ASEISMIC RIDGES AND SEA-FLOOR PLATEAU IN THE INDIAN OCEAN |
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Wang Shugong, Gao Yang
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First Institute of Oceanography, SOA, Qingdao, 266003
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| Abstract: |
| From October, 1986 to May, 1987 Chinese scientists carried out their third Antarctic scientific expedition and first round the world scientific investigation, during which a amount of marine gravity data were obtained by the geophysists from the First Institute of Oceanography (FIO), State Oceanic Administration (SOA). These data filled in their data gap in the Atlantic and Indian Ocean. Based on the data a Preliminary study has been made in this paper on the gravity anomalies of the aseismic ridges, sea-floor plateaus and the Mid-Ridge of the Indian Ocean. The results suggest that the aseismic ridges, sea -floor plateau and Mid-Ocean Ridge exist with a low value zone of Bouguer anomalies. However the reasons causing the low Bouguer anomalies are different. The former two have a crust thickening, a Moho discontinuity arching down and asthenosphere deepening. So the low value zone may be mainly caused by an anti-root lying beneath them. On the contrary in the later case of the Mid-Ocean Ridge the crust is becoming thinner, Moho arching up and asthenosphere lifting. So an anomalous mantle with high temperature, low velocity and low density may be main reason of the low Bouguer anomalies. The strong teconic activities of the Mid-Ocean Ridge system seem to be driven by a thermodynamics of the mantle. Although the crust of the Mid-Ocean Ridge is new, its activity has a long history and has reached to a balance state in thermodynamics. There is almost no doubt that the free-air anomalies of the low amplitude on the Mid-Ocean Ridge mean a lifting of the mantle material with a low velocity and low density, but can not be seen approximately as a first-order of isostatic anomaly. The Mid-Ocean Ridge can not be concluded to be in an equilibrium state, either. The studies mentioned above have provided with an important basis for the further researches on deep tectogenesis, equilibrium state and dynamic mechanism of the tectonic belts in the Indian Ocean and will be of far reaching importance to the further approach to the formation and evolution of the Indian Ocean. |
| Key words: Aseismic ridge, Sea-floor plateau, Mid-Indian Ridge, Gravity anomalies, Deep tectogenesis |
