Development of stepwise laser spot demagnetization system and itsapplication to planetary geology

步进式激光光斑退磁系统的研制及其在行星地质中的应用

基本信息

批准号：
19684017
负责人：
NAKAMURA Norihiro
金额：
$ 16.31万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Young Scientists (A)
财政年份：
2007
资助国家：
日本
起止时间：
2007 至 2009
项目状态：
已结题

项目摘要

I have been developing a stepwise laser spot demagnetization system for the application to the micro-paleomagnetic study of pre-Cambrian rocks, shocked crater rocks and meteorites. I employed a Q-switched 30W second harmonic generation Nd : YAG green laser, a digital 2-color pyrometer (300-1000℃) with quartz fiber optics of 600 micrometer and a two-way laser irradiation unit with CCD camera. This laser demagnetization system allows us to stepwisely heat the individual spot area in oriented thin sections. As a sample holder, I developed a X-Y stage controlled vacuum chamber with quartz glass viewport embedded into horizontally-lying 12-folded cylindrical silicon steel. The target sample is hold in a very weak ambient magnetic field of 25nT with 10^<-2>Torr vacuum condition. In addition to laser demagnetization system, I have conducted a micro-paleomagnetic study of shock melt veins in Tenham chondrite and fault gouge samples of Chelungpu fault and Nojima fault, by using a supersonic cutter blade. Through these studies, I found that shock melt veins are a reliable magnetic recorder of ambient field during ancient parent-body collisions, and fault gouge are also a reliable recorder for the earthquake faulting. Although these new techniques of laser demagnetization and micro-paleomagnetic study are powerful, the Pre-Cambrian rocks and meteorites have still suffered metamorphism for a long time scale. Traditional Neel theory of magnetization tells us that single domain magnetic particles relax its remanent magnetization to energetically stable condition in an exponential function of temperature and time. However, it is often that natural magnetization data is not consistent with the theory, being due to metamorphism. To interpret the natural data, I have extended the Neel theory to a stretched exponential function, and derived a new non-linear time-temperature relation for metamorphosed rocks and meteorites.

我一直在开发一个逐步的激光斑点消灭系统，以应用于夏布里岩石，震惊的火山口岩石和陨石的微磁磁研究。我采用了Q开关的30W第二次谐波生成ND：Yag Green Laser，一种数字2色高温计（300-1000℃），具有600千分尺的石英光纤和带有CCD摄像头的双向激光照射单元。这种激光脱氧化系统使我们能够在定向薄部分中加热单个点区域。作为样品支架，我开发了一个X-y级受控的真空室，石英玻璃视口将嵌入水平的12倍圆柱硅钢中。目标样品保持在非常弱的环境磁场的25nt，具有10^<-2>托尔真空状态。除了激光灭绝系统外，我还使用超音速切割器刀片对Chelungpu断层和NOJIMA断层的Tenham Conecontrite中的休克融化静脉进行了微磁性研究。通过这些研究，我发现冲击融化是古代父母碰撞期间环境场的可靠磁记录器，并且断层孔也是地震断层的可靠记录仪。尽管这些新技术的激光驱电和微磁磁研究非常有力，但前木岩和陨石仍然长期遭受变质。传统的磁化理论告诉我们，单个域磁颗粒在温度和时间的指数功能下放松了其remanent磁化的有效稳定条件。但是，自然磁化数据通常与该理论不一致，这是由于变质性引起的。为了解释自然数据，我将Neel理论扩展到了伸展的指数函数，并为变形岩石和陨石提供了新的非线性时间温度关系。

项目成果

期刊论文数量（0）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Direct identification of stable remanence carriors: MI magnetic microscopy with demagnetization tests

直接识别稳定剩磁载体：具有退磁测试的 MI 磁显微镜

DOI：
发表时间：
2007
期刊：
影响因子：
0
作者：
Uehara;M & Nakamura;N.
通讯作者：
N.

Shocked melt veins as recorders of paleomagnetic field for an asteroidal parent-body

冲击熔脉作为小行星母体古磁场的记录器

DOI：
发表时间：
2007
期刊：
影响因子：
0
作者：
Sato;Y. & Nakamura;N.
通讯作者：
N.

Coarse-grained magnetites in biotite as a possible stable remanence-carrying phase in Vredefort granites

黑云母中的粗粒磁铁矿作为 Vredefort 花岗岩中可能的稳定剩磁携带相

DOI：
发表时间：
2010
期刊：
GSA Special Paper "Large Meteorite Impacts and Planetary Evolution IV" (in press)
影响因子：
0
作者：
N. Nakamura;Okuno;K.;Uehara;M.;Ozawa;T.;Tatsumi-Petrocholis;L.;Fuller;M.
通讯作者：
M.

Nonlinear thermoremanence corrections for Thellier paleointensity experiments on single plagioclase crystals with exsolved magnetites : a case study for the Cretaceous Normal Superchron

对带有出溶磁铁矿的单个斜长石晶体的泰勒古强度实验的非线性热剩磁校正：白垩纪正常超年代的案例研究