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对地壳岩石的弹性性质进行了研究。我们已经开发了在中低地壳压力和温度条件下进行超声波测量的技术。这些技术现已被用于研究主要的地壳岩石，包括辉长岩、英云闪长岩、花岗岩、斜长岩、麻粒岩和角闪岩，这些岩石来自(1)日本中部坦泽山和巴基斯坦科希斯坦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，(3)南极东部的太古宙超高温麻粒岩相杂岩(纳皮尔杂岩)和泛非造山带(Lutzow-Holm杂岩)。为了解释岛弧东北本州弧的地震结构，将在低于中下地壳温度下测得的Vp值与遵循温度导数给出的…调整到25℃的地震速度剖面进行了比较Rudnick和Fountain(1995)的More En，并采用地温梯度(Nishimoto等人，2005年)。为了直接与深岛弧压力和温度下的地震速度进行比较，我们开发了使用缓冲杆技术的超声波速度测量方法。这些测量将以前对岩石进行超声波测量的温度范围扩大了一倍。采用PT缓冲杆将换能器与高温环境隔离。用脉冲反射技术测定了岩石样品的旅行时间。河野等人(2004A)测量了辉长岩、辉石麻粒岩、辉长岩和辉长岩的纵波速度(Vp)，发现在下地壳岩石中Vp的温度导数的不连续变化是这种可逆的和不连续的变化，这是以前提出的热破裂、脱水反应和/或部分熔融等机制难以解释的。数据表明，这种可逆和不连续的变化可能与斜长石的相变有关(Kono等人，2004b)。较少

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