| ZHANG Tao,GAO Jinyao,CHEN Mei,YANG Chunguo,SHEN Zhongyan,ZHOU Zhiyuan,WU Zhaocai,SUN Yunfan.Mantle melting factors and amagmatic crustal accretion of the Gakkel ridge, Arctic Ocean[J].Acta Oceanologica Sinica,2015,34(6):42-48 |
| 北冰洋Gakkel洋中脊的地幔熔融控制因素及非岩浆地壳增生 |
| Mantle melting factors and amagmatic crustal accretion of the Gakkel ridge, Arctic Ocean |
| 投稿时间：2014-05-26 修订日期：2014-09-10 |
| DOI：10.1007/s13131-015-0686-8 |
| 中文关键词: Gakkel洋中脊 剩余地幔布格重力异常 地壳厚度 湿熔融 非岩浆地壳增生 |
| 英文关键词:Gakkel ridge residual mantle bouguer anomaly crustal thickness wet melting amagmatic accretion |
| 基金项目:Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract Nos CHINARE 2013-03-03 and 2013-04-03; the National Natural Science Foundation of China under contract No. 41106049. |
| 作者 | 单位 | E-mail | | 张涛 | 国家海洋局第二海洋研究所, 杭州 310012
国家海洋局海底科学重点实验室, 杭州 310012 | zhangtaosio@gmail.com | | 高金耀 | 国家海洋局第二海洋研究所, 杭州 310012
国家海洋局海底科学重点实验室, 杭州 310012 | | | 陈美 | 浙江华东建设工程有限公司, 杭州 310030 | | | 杨春国 | 国家海洋局第二海洋研究所, 杭州 310012
国家海洋局海底科学重点实验室, 杭州 310012 | | | 沈中延 | 国家海洋局第二海洋研究所, 杭州 310012
国家海洋局海底科学重点实验室, 杭州 310012 | | | 周志远 | 同济大学海洋与地球科学学院, 上海 200092 | | | 吴招才 | 国家海洋局第二海洋研究所, 杭州 310012
国家海洋局海底科学重点实验室, 杭州 310012 | | | 孙运凡 | 国家海洋局第二海洋研究所, 杭州 310012
国家海洋局海底科学重点实验室, 杭州 310012 | |
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| 中文摘要: |
| 扩张速率是控制全球洋中脊地幔熔融和构造活动的一级因素。Gakkel洋中脊的扩张速率从西往东逐步变小, 但是地壳厚度却依次分为厚薄相间的四个区域。这表明, Gakkel洋中脊区域地幔熔融和扩张速率却并不完全相关, 地幔温度、地幔含水量和地幔物质组成等其它因素在地壳增生中起到了重要作用。参照重力反演地壳厚度, 本文利用湿熔融模型推断出Gakkel洋中脊下的四个区域分别对应1270℃、1220℃、1280℃和1280℃的地幔位势温度(假定全球平均地幔含水量), 或者210 ppm、0 ppm、340 ppm以及280 ppm的地幔含水量(假定1260℃地幔位势温度)。西部地壳减薄区对应低温地幔, 而其它三个区域主要受到扩张速率减慢导致的传导作用增加的影响。沿Gakkel洋中脊, 地壳厚度和岩石采样类型具有良好的一致性。在地壳厚度小于1.5 km的区域, 岩石采样几乎全部为蛇纹岩化橄榄岩;在地壳厚度大于2.5 km的区域, 岩石采样几乎全部为玄武岩;在地壳厚度为1.5-2.5 km的区域, 岩石采样中混杂了各类岩石。依据此一致性, Gakkel洋中脊传统的岩浆增生区域仅占44%, 非岩浆增生区域占到29%的区域, 非岩浆的扩张方式在超慢速洋中脊的形成过程中起了重要作用。 |
| 英文摘要: |
| Spreading rate is a primary factor of mantle melting and tectonic behavior of the global mid-ocean ridges. The spreading rate of the Gakkel ridge decreases gradually from west to east. However, the Gakkel ridge can be divided into four thick-and-thin zones with varying crustal thicknesses along ridge axis. This phenomenon indicates that mantle melting of the Gakkel ridge is not a simple function of spreading rate. Mantle temperature, water content, mantle composition, and other factors are important in crustal accretion processes. Based on gravity-derived crustal thickness and wet melting model, we estimate that the mantle potential temperatures of the four zones are 1 270, 1 220, 1 280, and 1 280℃ (assuming that mantle water content equals to global average value), with corresponding mantle water contents of 210, 0, 340, and 280 mg/kg (assuming that mantle potential temperature is 1 260℃), respectivly. The western thinned crust zone is best modeled with low mantle temperature, whereas the other zones are mainly controlled by the enhanced conduction caused by the slower spreading rate. Along the Gakkel ridge, the crustal thickness is consistent with rock samples types. Predominated serpentinized peridotite and basalt are found in the area with crustal thickness <1.5 km and >2.5 km, respectively. The rock samples are including from basalt to peridotite in the area with crustal thickness between 1.5 and 2.5 km. Based on this consistency, the traditional magmatic accretion zone accounted for only 44% and amagmatic accretion accounted for 29% of the Gakkel ridge. The amagmatic accretion is a significant characteristic of the ultra-slow spreading ridge. |
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