塔里木西南缘下地壳低速层的成因:斜长角闪岩的纵波速度和衰减的限制 |
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引用本文: | 岳兰秀,谢鸿森,刘丛强,刘永刚.塔里木西南缘下地壳低速层的成因:斜长角闪岩的纵波速度和衰减的限制[J].地球与环境,2003,31(3):13-19. |
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作者姓名: | 岳兰秀 谢鸿森 刘丛强 刘永刚 |
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作者单位: | 1. 中国科学院地球化学研究所,贵州,贵阳550002;中国科学院研究生院,北京100039 2. 中国科学院地球化学研究所,贵州,贵阳550002 |
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基金项目: | 国家自然科学基金(10299040和49902020),中国科学院创新项目(KJCX-N12) |
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摘 要: | 在1 0GPa,室温~1200℃条件下,测量了新疆库地地区斜长角闪岩的纵波速度(Vp)和品质因子(Q值),得出在1 0GPa恒压下,Vp和Q值随温度和深度的变化关系。结果显示,Vp和Q值随温度的升高而下降,观察实验样品并结合Vp和Q值与熔体含量的关系,发现部分熔融是影响Vp和Q值变化的主要因素。依据实验结果,并结合区域上压力梯度和温度梯度资料计算了Vp和Q值随深度的变化。结果表明Vp和Q值先随深度的增加而缓慢增大,在32km左右开始突然减小,表明开始出现低速层。结合温度和熔体含量的关系得出,低速层的出现可能是部分熔融的结果。塔里木及周边地区的地震测深以及地震反演的结果也显示,在相同的温度和压力条件下,地壳内部32~44km的范围内存在低速层,同时高温高压的实验结果与阿拉木图地区的Vp值相当一致,可以推测塔里木西南缘下地壳的岩石成分中含有斜长角闪岩。
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关 键 词: | 斜长角闪岩 高温高压 纵波速度 弹性波衰减 部分熔融 下地壳低速层 |
文章编号: | 1008-0244(2003)03-0013-07 |
修稿时间: | 2002年10月8日 |
ORIGIN OF LOW-VELOCITY LAYER IN THE LOWER CRUST OF SOUTHWEST TARIM: LIMITS OF VELOCITY AND ATTENUATION FOR PLAGIOCLASE AMPHIBOLITE |
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Abstract: | Compressional wave velocity (Vp) and attenuation (Q) in amphibolite collected from Kudi, Xinjiang, were measured at high pressure (10 GPa) and high temperature (up to 1200℃) The experimental results showed that Vp and Q values decrease with increasing temperature, reflecting that Vp and Q are influenced by partial melting The relationship of Vp and Q with depth, in the light of the correlations between Vp and Q and temperature and pressure, shows that Vp and Q increase with depth The tendency of increasing is the same as that obtained by seismological studies The low velocity layer appears at the depth of 32km, at which the Vp and Q decrease rapidly Seismic study in Tarim and its vicinity yielded the same result The low velocity layer is measured from 32km to 44km in the Kuytun, Tianshan and Alamtu areas So it may be concluded that amphibolite probably exits in the lower crust of Southwest Tarim And partial melting is the main reason for the existence of the lower velocity layer |
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Keywords: | plagioclase amphibolite high temperature and high pressure partial melting compressional velocity attenuation low-velocity layer in the lower crust |
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