P and S wave velocities of deep crustal rocks under high pressure and high temperature conditions

我们利用超声波测量技术对地壳岩石的弹性性质进行了研究。我们已经开发出在中低地壳压力和温度条件下进行超声波测量的技术。这些技术现已应用于研究主要地壳岩石，包括辉长岩、英云闪长岩、花岗岩、斜长岩、麻粒岩和角闪岩，它们取自（1）日本中部的Tanzawa山和巴基斯坦的Kohistan地区的岛弧地壳深部剖面，（2）日本东北部的Ichinomegata，日本西南部的Takashima和Kurose，东南极太古宙超高温麻粒岩相杂岩（纳皮耶杂岩）和泛非造山带（Lutzow-Holm杂岩）。为了解释本州岛弧东北部的地震结构，将在比中下地壳温度低的温度下测得的Vp值与地震速度剖面进行了比较。 ...更多信息 由Rudnick和Fountain（1995）提出并采用地热梯度（Nishimoto等人，2005年）。为了直接比较地震速度在深岛弧的压力和温度，我们开发了超声波速度测量使用缓冲棒技术。这些测量使以前对岩石进行超声波测量的温度范围翻了一番。铂缓冲棒用于将压电换能器与高温环境隔离。通过岩石样品的旅行时间用脉冲反射技术测定。Kono等人（2004 a）测量了辉长岩、辉石麻粒岩、韦尔岩和镁橄榄石在1 GPa下的压缩波速度（Vp），最高可达1000□，并发现下地壳岩石中Vp的温度导数的不连续变化。这种可逆和不连续的变化难以用先前提出的机制（如热裂解、脱水反应和/或部分熔融）来解释。这些数据表明，这种可逆和不连续的变化与斜长石的相变有关（Kono等人，2004 b）。少

We carry out research on the elastic properties of the crustal rocks using ultrasonic measurements. We have developed techniques to perform ultrasonic measurements at mid-to-lower crustal conditions of pressure and temperature. These techniques are now been applied to study the major crustal rocks, including gabbro, tonalite, granite, anorthosite, granulite and amphibolite, which were collected from (1)island arc deep crustal sections of Tanzawa Mountain of central Japan and Kohistan area of Pakistan, (2)Ichinomegata of NE Japan, Takashima and Kurose of SW Japan, and (3)Archean ultra-high temperature granulite-facies complex (Napier Complex) and Pan-African erogenic belt (Lutzow-Holm Complex) of East Antarctica. In order to interpret seismic structure of island arcs NE Honshu arc, the Vp values measured at lower temperatures than those of mid-to-lower crusts were compared with the seismic velocity profiles which were adjusted to value at 25 □ by following the temperature derivative giv … More en by Rudnick and Fountain (1995) and employing the geothermal gradient (Nishimoto et al.,2005). In order to compare directly to seismic velocities at the deep island arc pressures and temperatures, we developed ultrasonic velocity measurements using buffer rod technique. The measurements have doubled the temperature range of previous ultrasonic measurements on rocks. Pt buffer rod is used to isolate the piezoelectric transducer from the high-temperature condition. Travel times through the rock sample were determined with the pulse reflection technique. Kono et al.(2004a) measured compressional wave velocities (Vp) of gabbronorite, pyroxene granulite, wehrlite and websterite up to 1000□ at 1 GPa and found discontinuous change in temperature derivative of Vp in lower crustal rocks arc This reversible and discontinuous change is difficult to explain by the previously proposed mechanisms, such as thermal cracking, dehydration reaction, and/or partial melting. The data suggest that this reversible and discontinuous change would be associated with phase transition in plagioclase (Kono et al.2004b). Less