西藏申扎地区晚古生代地层岩石磁学研究

目的研究西藏申扎地区晚古生代地层载磁矿物特征,为构造磁学等提供依据。方法运用饱和等温剩磁(SIRM),三轴等温剩磁(SIRM)热退磁,磁化率-温度(χ-T)曲线和NRM热退磁实验等方法进行综合分析。结果中—上二叠统样品中含较多针铁矿、赤铁矿;下二叠统和石炭系样品中以磁铁矿为主;泥盆系样品中富集铁硫化物。结论该套沉积地层中具有不同磁学特征的磁性矿物共生组合,可能导致岩石剩磁获得过程相对复杂;剖面上磁性矿物组合的变化,蕴含着沉积环境演化的信息。     

菱铁矿热处理后的异常等温剩磁特征

菱铁矿经热处理后在室温下测定的等温剩磁曲线形态，与热处理温度有关。经过５００－７００℃温度范围内热处理的样品，等温剩磁曲线呈现与普通铁磁质的等温剩磁曲线不同特征。反常曲线的详细形态与磁化经历有关。从零剩磁态出发，逐渐增加磁化场直到３００ｍＴ，在几十毫特斯拉段，剩磁出现一个峰，以后逐渐趋于一个稳定值。再来回施加反向和正向外磁场时，在四个象限内出现高度相等的峰。在第一和第三象限内，峰之后为一坪区。坪高     

岩石圈居里等温面解释的若干问题

介绍了利用区域磁测资料计算居里等温面的同种常用方法，对影响居里等温面的几个重要因素，诸如区域异常的选择，滑动窗口的尺度选择等进行了理论分析，根据影响岩石居里温度的各种因素，提出评估居里等温面计算精度的方法，给出居里等温面在区域负磁异常起因，油气资源预测，成矿作用与物性界面关系等方面的应用。     

功率谱法反演青藏高原居里等温面

应用NGDC-720-V3地磁场模型,计算得到青藏高原岩石圈磁异常数据,经过滤波、微分化极后,根据径向平均功率谱反演法得到青藏高原居里等温面深度分布.结果表明,这一地区居里等温面深度在23~42 km.研究还表明,青藏高原居里等温面的深度分布与该区的地质构造和地壳热结构具有一定的对应关系.     

Fe纳米线阵列宏观磁性的Preisach模拟

采用阳极氧化铝模板法制备16nm的铁纳米线阵列膜,并研究了其宏观磁学性质.沿着纳米线长轴加场测得的磁滞回线表现出高的矫顽力和矩形比,归因于垂直于膜面的高形状各向异性.等温剩磁曲线和直流退磁曲线的测量结果表明纳米线阵列体系中存在强烈的退磁性相互作用.采用Preisach模型对相关曲线进行模拟,发现剩磁矫顽力和相互作用场的分布较窄,是一种典型的符合双势垒模型的体系.     

从一条PFA热降解DSC曲线推算其等温热稳定性

利用一条非等温的ＤＳＣ曲线，从研究ＰＦＡ热降解的最可几反应机制及其活化能入手，推导出在等温条件下反映热稳定性的降解率，温度和时间之间的简单关联式。结合红外光谱对ＰＦＡ热降解过程作初步探讨。     

环境磁学磁性参数简介

环境磁学是一门能为全球环境变化、气候过程和人类活动对环境的影响等研究提供有价值的资料的边缘新兴学科。目前比较常用的磁学参数有磁化率、频率磁化率、天然剩磁、饱和等温剩磁、剩磁矫顽力、非磁滞剩磁等等，它们用途广泛，其测量既简便又快速，可为重建古环境、恢复古气候提供可靠的依据。     

西菲律宾海沉积物的岩石磁学性质及其古环境意义

对位于西菲律宾海黑潮源区的Ph05重力柱样沉积物进行了详细的岩石磁学测量,包括磁化率、非磁滞剩磁、等温剩磁,以及典型样品的磁化强度随温度变化特征和磁滞参数等.结果表明主要载磁矿物为低矫顽力的磁铁矿,含有少量高矫顽力磁性矿物.磁性矿物的含量变化不大,磁性颗粒以准单畴为主.磁性矿物主要为碎屑成因而非生物成因,磁性矿物的粒度敏感地记录了近250 ka来的气候变化并表现出冰期-间冰期旋回,即在冰期时磁性矿物的粒度变粗,而在间冰期磁性矿物的粒度变细.XARM/X参数与氧同位素曲线及温跃层深度等的变化具有对应性,这种对应性表明磁性矿物粒度参数可以反映上部水体的变化,从而为反演黑潮演化提供了新的手段.     

西菲律宾海沉积物的岩石磁学性质及其古环境意义

对位于西菲律宾海黑潮源区的Ph05重力柱样沉积物进行了详细的岩石磁学测量,包括磁化率、非磁滞剩磁、等温剩磁,以及典型样品的磁化强度随温度变化特征和磁滞参数等．结果表明主要载磁矿物为低矫顽力的磁铁矿,含有少量高矫顽力磁性矿物．磁性矿物的含量变化不大,磁性颗粒以准单畴为主．磁性矿物主要为碎屑成因而非生物成囚,磁性矿物的粒度敏感地记录了近250ka来的气候变化并表现出冰期一间冰期旋回,即在冰期时磁性矿物的粒度变粗,而在间冰期磁性矿物的粒度变细．XARM／x参数与氧同位素曲线及温跃层深度等的变化具有对应性,这种对应性表明磁性矿物粒度参数可以反映上部水体的变化,从而为反演黑潮演化提供了新的手段,     

Fe0.72Ni0.28纳米线阵列的制备与剩磁特性研究

利用电化学沉积的方法,在多孔氧化铝模板中成功制备出直径为50 nm,长度约4 μm的Fe0.72Ni0.28合金纳米线阵列.X射线衍射表明其结构为体心立方结构;等温剩磁曲线和直流退磁曲线表明在纳米线中,磁化较难,而退磁容易,而且组成纳米线的小粒子之间存在退磁性的相互作用.     

Magnetic properties of street dust and topsoil in Beijing and its environmental implications

Environmental magnetic measurements were carried out on the sanrhples of street dust and topsoil, which were collected along the roadway in the urban and suburb of Beijing, including magnetic susceptibility （X）, anhysteretic remanent magnetization （ARM）, isothermal remanent magnetization （IRM） of all samples and temperature-dependence of magnetic susceptibilities and magnetic hysteresis parameters of representative samples. Obvious differences exist between the samples of street dust and those of topsoil. Compared with topsoil samples, the concentration of magnetic particles and high-coercivity components in street dust samples are higher, and the magnetic grains are coarser. Both dust and topsoil samples are dominated by ferrimagnetic minerals, and iron particles are only detected in some dust samples. These results suggest that street dust samples reflect the characteris- tic of particles produced by industrial and traffic activities, and the magnetic property of topsoil sam- ples represents the characteristic of particles from both anthropogenic and natural sources. The distribution of magnetic parameters is influenced by the environment where the samples are collected, like industry, traffic density and other road conditions. Hard isothermal remanent magnetization （HIRM） may be used as an indicator of particles produced by traffic activity. Dust storm samples collected on 17 and 18 April, 2006 have different magnetic properties from street dust and natural particles, like loess and paleosol, which indicate that the dust storm might be mixed with anthropogenic particulates during transport and falling.     

东鞍山浮选尾矿预富集精矿悬浮磁化焙烧试验研究

为实现东鞍山铁矿石浮选尾矿的资源化利用,对浮选尾矿预富集精矿开展了悬浮磁化焙烧试验研究.结果表明,浮选尾矿预富集精矿主要矿物组成为赤褐铁矿、磁铁矿、菱铁矿和石英,TFe品位为31.13%.浮选尾矿预富集精矿适宜的悬浮磁化焙烧工艺参数为:气体流量600mL/min,氢气体积分数20%,焙烧温度520℃,焙烧时间20min.焙烧产品经弱磁选可得铁精矿的TFe品位为64.23%,回收率为79.53%.焙烧产品的铁物相,XRD,VSM分析表明,经过悬浮磁化焙烧后,原矿中赤褐铁矿和碳酸铁转变为磁铁矿,矿石的饱和磁化强度和磁化率增强.     

东鞍山含碳酸盐铁矿石悬浮磁化焙烧试验

介绍了一种半工业试验用悬浮焙烧设备,并考察了焙烧温度、还原气体CO及流化气体N₂用量对东鞍山含碳酸盐铁矿石预富集粗精矿悬浮焙烧效果的影响.试验结果表明,在焙烧温度540℃,还原气体CO用量4m³/h及流化气体N₂用量2m³/h的条件下,焙烧物料经磨矿-磁选后可获得铁品位66.1%,回收率91.2%的铁精矿.铁的化学物相、光学显微结构及穆斯堡尔谱分析表明,经悬浮焙烧后弱磁性的菱铁矿和赤铁矿转化为了强磁性的磁铁矿,部分结晶粒度较粗(>100μm)的赤铁矿仅颗粒表面转变为磁铁矿,但这种Fe₂O₃@Fe₃O₄核壳结构的新生磁铁矿由于磁性较强,在后续磁选过程中依然能够得到有效的回收,并不会影响分选效果.     

垂直磁记录薄膜交换耦合作用及开关场分布的测量

采用Lakeshore7407型振动样品磁强计,以Co-Pt垂直磁记录薄膜为例,详细介绍了垂直薄膜等温剩磁(isothermalremanentmagnetization,IRM)曲线、直流退磁剩磁(directcurrentdemagnetizationremanence,DCD)曲线的测量方法和退磁因子的计算方法,并给出根据退磁场修正后的IRM和DCD曲线计算垂直磁记录薄膜曲线和开关场分布(SFD)的方法.最后详细讨论了薄膜的微观组织和易磁化轴取向分布对退磁场、交换耦合作用和SFD的影响.结果表明:退磁场的存在使得直接测量得到的晶粒间交换耦合作用偏小,开关场分布宽化;影响晶粒间交换耦合作用的内在原因是介质的微观组织和易磁化轴的取向分布.     

伊辛自旋梯的磁化平台和热力学性质研究

利用传递矩阵方法严格求解了混自旋S=1和S=3/2组成的伊辛自旋梯,考察了系统的磁化过程及外磁场下各向异性对系统热力学性质的影响.发现系统最近邻为铁磁性交换作用,链间次近邻为反铁磁性作用时,系统的磁化强度在m=1/4和m=3/4处出现磁化平台现象,与量子模型中的磁化平台可能出现的位置一致.系统的磁比热和磁化率曲线中出现了新颖的双峰现象.     

Magnetic granulometry of recent sediments from the Huguang Maar and its implication for provenience

To understand the origin and its climatic implications of the Huguang Maar sediments, we conducted laser grain size analysis and rock mangtic measurement for the recent deposits from the Huguang Maar and for the volcanic rocks of the caldera for comparison. The grain size distributions are dominated by clayey silts for both the bulk sediments and magnetic separates. Acquisition of isothermal remanent magnetization (IRM) and thermal demagnetization of IRM suggest (titano) magnetite as the dominating magnetic mineral in the sediments; high coercivity minerals are not detected. Therefore, the ratio of the susceptibility of anhysteretic remanent magnetization (k _ARM) to the weak field magnetic susceptibility (k), k _ARM/k can be used to estimate the grain size of magnetite. The sediments and volcanic rocks yield values of 13.7 and 11.8 for the k _ARM/_k, respectively, corresponding to grain size values of ～0.03 µm and ～0.05 µm. The magnetic granulometry of lake sediments is distinctive from one of the Chinese loess, in which published data suggest a value of 6.0 for k _ARM/_k, and grain size of ～0.1 µm, but is akin to the nearby volcanic rocks. Although a Loess Plateau source of the lake sediments cannot be fully ruled out, the catchment is most probably the main source. We explain the slightly finer magnetite grain size in sediments than in the volcanic rocks as being disintegrated of particles during erosion and transportation. We conclude that there is no evidence for aeolian input of the Loess Plateau dusts into the Huguang Maar, and the relationship between magnetic parameters of the lake sediments and winter monsoon intensity is probably more complicated than previously thought.     

Paleomagnetism of early Paleozoic volcanic rocks from the Beishan area,Gansu of northwest China: Preliminary insight into early Paleozoic kinemics of the Beishan terrane

We report rock magnetic and paleomagnetic results for Middle Silurian Gongpoquan and Middle Ordovician Huaniushan volcanic samples collected from the Mazongshan and Hongliuyuan areas of Gansu Province, northwest China. The resultsindicate that the main magnetic mineral of the Gongpoquan and Huaniushan volcanic rock is magnetite, and it may remain characteristic remanent magnetization acquired at the time of formation of the rocks. However, with the exception of samples from site go20, most of Middle Ordovician Huaniushan volcanic samples have a very weak nature remanent magnetization, and generally show an erratic demagnetization behavior, which does not allow isolation of characteristic remanent magnetizations from these samples. Comparison of paleomagnetic results obtained from the Beishan area of Gansu with Paleozoic apparent polar wander paths for Tarimand Siberia suggests that the Beishan tarrane, the southern part of the Beishanarea of Gansu beyond the Mingshui-Shipanjin-Xiaohuang- shan zone, and adjacent Tarim block and Siberia plate could not have been connected in their present configuration by the Middle Silurian time. On the other hand, we infer that the early Paleozoic Mingshui-Shipanjin-Xiaohuangshan oceanic basin may open from west to east during period from the Ordovician to Silurian, and the post-Middle Silurian closing of this oceanic basin may result from a progressed eastward scissor-like rotation.     

Remanence acquisition and its alteration on sediments

Previous palaeomagnetic work shows that the mechanism of remanence acquisition on sediments is very complicated. Different magnetizing processes under different conditions may produce some anomalous magnetic signals which have nothing to do with the changes of the geomagnetic field and are difficult to explain. The depositional remanent magnetization (DRM) may produce an inclination error and a bedding error, while postdepositional remanent magnetization (PDRM) may result in a time delay between the magnetic and sedimentary ages. When there are some different magnetic phases with different lock-in depths in the sediments, it is difficult to judge the depth of the reversal or excursion, or even the artificial magnetic signal may be produced. Even if there is only one magnetic phase in the sediment, the recorded magnetic signals may also be different if the lock-in depth is changed comparative to the lasting period of one reversal or excursion. Demagnetization may also change the primary magnetic records and the changes of water content may result in the displacement of magnetic boundary. The so-called “unstable core”, representing subtle changes in mineralogy into and out of a self-reversal region or a viscous magnetization region, gives a complicated palaeornagnetic record with many apparent changes in the palaeomagnetic direction. Moreover, some physical disturbances, such as biodisturbance, deformation, drilling processes and drying effects, may result in the remanence alteration. Some palaeomagnetic investigations demonstrate that good magnetic signals are invariably achieved on homogenous mud or clay sediments, but the worse signals on inhomogeneous profiles, especially on sandy layers.     

由沉积物中准同生构造的褶皱展平试验确定沉积剩磁固化深度

上新世湖心相页岩中准同生构造的褶皱展平试验揭示,这套沉积物中的剩磁固化于这些准同生构造形成之后,固化深度大于10-15cm。这一事实与模拟实验结论的之间矛盾表明,由于天然过程的进行速率慢得无法与实验室过程比拟,天然沉积物中沉积后碎屑剩磁的作用要比模拟实验的绪论强得多。将模拟实验得出的关于磁性颗粒重新排列条件的定量结论简单地外推到天然过程是不适当的。任何关于沉积物获得剩磁的模型都必须接受以天然过程为基础的检验,仅有实验室内的模拟试验是很不够的。     

滇中昆阳群古地磁研究

对昆阳群中采集的２８３块样品用热退磁法做了磁清洗处理,经精度检验,进行了统计分析．根据获得的古地磁结果,探讨了昆阳群地层所代表的古地磁极性和古纬度,建立了该地区中、晚元古界古地磁视极移路径,并与华北地块及扬子地块该时期的视极移路径进行了对比,讨论了其构造运动及相互之间的关系,认为下昆阳亚群与长城系古纬度相近,古地磁极性及视极移路径可比,时代相当．