橄榄石原位高温拉曼光谱研究

利用微型电阻丝加热装置产生高温, 采用镍铬热电偶探测样品的温度, 在273～1 113 K温度范围,对橄榄石晶体进行了原位高温拉曼光谱研究。拉曼光谱数据显示：Si-O伸缩振动模高于800 cm^-1,Si-O弯曲振动模为400～700 cm^-1,SiO₄四面体旋转振动模和金属-氧的平移振动模低于400 cm^-1;得到了橄榄石拉曼振动频率随温度的变化关系,首次发现了橄榄石常温频率为541 cm^-1的Si-O反对称弯曲振动的A_g模,比其它的振动频率有较弱的温度效应。     

黑龙江省多宝山-宽河成矿带Cu-Au成矿规律与成矿预测

黑龙江省多宝山-宽河成矿带铜金矿产十分丰富.区内于早奥陶世初形成的"四隆四拗"构造格局控制了以后各地质时期地层、岩浆演化及矿产的分布.通过对矿带成矿地质背景、物化探异常、典型矿床特征的分析与归纳,总结了铜金成矿规律、成矿条件与找矿标志,预测出9个找矿重点靶区.     

海浪谱峰周期与跨零周期的一个经验关系式

从PM谱出发,推导出谱峰周期与跨零周期的谱关系式Tp=(5π/4)^1/4Tz≈1．41Tz;对海上实测海浪谱资料进行了分析,表明该式所给出的系数与统计值相当接近,较好地解决了由海浪谱直接获取谱峰周期所产生的谱稳定性问题。     

广西各地的雨季开始与汛期雨量分布型的分析

统计分析了广西各地雨季开始日的时空分布特点,指出江南极锋雨带南移使广西雨季自北向南相继开始,NE季风与SE季风共同作用使广西雨季东部先于西部,地处云贵高原余脉、右江上游的百色,雨季的开始与南海热带季风爆发有关.分析了广西各地主汛期雨量分布的"单峰型"和"双峰型"形成原因以及单双峰型的转换机理,指出影响广西的热带气旋频数大小的变化,是后汛期峰值时隐时现的主要原因.对全区性雨季偏早或偏迟年份的雨量和雨量分布型也作了对比分析,所揭示的相关事实,对天气预测有一定参考意义.     

不同荷载作用下拉破裂的声发射特征研究

采用类岩石材料研究了不同加载条件下的张拉裂纹的破裂过程,并利用声发射(AE)测试技术分析了劈拉试样和三点弯曲试样在断裂过程中裂纹的萌生、起裂、扩展和破裂全过程的声发射特征。试验结果表明,声发射的阶段性突发特征反映了张拉裂纹阶段性扩展的力学机制。但是,在不同的加载条件下,张拉破裂的声发射特征有所差异：在弯拉应力作用下,试样拉破裂的声发射特征表现可分为声发射数的渐进增长、快速增长、突发式增长和逐渐下降4个阶段;而在劈拉应力作用下,试样破裂的声发射特征可分为声发射数缓慢增长、声发射数突发和声发射数的稳定发展3个阶段。在弯拉应力作用下,裂纹的萌生和聚集阶段的声发射特征明显,但在劈拉应力作用下几乎观察不到其声发射特征变化。不同破裂模式下的声发射特征值得进一步研究。     

爆破振动对砂浆锚杆的影响研究

爆破振动对锚杆有不利影响,运用应力波理论,并利用波函数展开法,研究了爆炸应力波与锚杆的相互作用过程,给出了爆破振动作用下砂浆锚杆周围砂浆体中的动应力和峰值振速分布情况,比较了不同频率应力波对锚杆的影响,导出了不同频率应力波作用下砂浆锚杆的安全质点振速范围。研究结果表明：入射波频率越高,砂浆锚杆所允许的安全质点峰值振速越大。     

P–T–t path of the Hercynian low-pressure rocks from the Mandatoriccio complex (Sila Massif, Calabria, Italy): new insights for crustal evolution

The tectono‐metamorphic evolution of the Hercynian intermediate–upper crust outcropping in eastern Sila (Calabria, Italy) has been reconstructed, integrating microstructural analysis, P–T pseudosections, mineral isopleths and geochronological data. The studied rocks belong to a nearly complete crustal section that comprises granulite facies metamorphic rocks at the base and granitoids in the intermediate levels. Clockwise P–T paths have been constrained for metapelites of the basal level of the intermediate–upper crust (Umbriatico area). These rocks show noticeable porphyroblastic textures documenting the progressive change from medium‐P metamorphic assemblages (garnet‐ and staurolite‐bearing assemblages) towards low‐P/high‐T metamorphic assemblages (fibrolite‐ and cordierite‐bearing assemblages). Peak‐metamorphic conditions of ～590 °C and 0.35 GPa are estimated by integrating microstructural observations with P–T pseudosections calculated for bulk‐rock and reaction‐domain compositions. The top level of the intermediate–upper crust (Campana area) recorded only the major heating phase at low‐P (～550 °C and 0.25 GPa), as documented by the static growth of biotite spots and of cordierite and andalusite porphyroblasts in metapelites. In situ U–Th–Pb dating of monazite from schists containing low‐P/high‐T metamorphic assemblages gave a weighted mean U–Pb concordia age of 299 ± 3 Ma, which has been interpreted as the timing of peak metamorphism. In the framework of the whole Hercynian crustal section the peak of low‐P/high‐T metamorphism in the intermediate‐to‐upper crust took place concurrently with granulite facies metamorphism in the lower crust and with emplacement of the granitoids in the intermediate levels. In addition, decompression is a distinctive trait of the P–T evolution both in the lower and upper crust. It is proposed that post–collisional extension, together with exhumation, is the most suitable tectonic setting in which magmatic and metamorphic processes can be active simultaneously in different levels of the continental crust.     

Origin and thermometry of graphites from Itapecerica supracrustal succession of the southern Sao Francisco Craton by C isotopes,X-ray diffraction,and Raman spectroscopy

ABSTRACT

In the mines of the Nacional de Grafite Company around Itapecerica (Minas Gerais), located in the southern Sao Francisco Craton, occurs a supracrustal succession of high-grade metamorphic rocks including quartzite, garnet-biotite gneiss, and graphite schist formed in the Palaeoproterozoic (2.0 Ga). During metamorphic processes, organic matter was progressively transformed into graphite. From four graphite samples of three different mines (two samples from high-grade metamorphic graphite schist and two generated by hydrothermal recrystallization of the graphite schist), the origin and formation temperature of this mineral was obtained by C isotopes, X-ray diffraction (XRD), and Raman spectroscopy. The values of δ¹³C range between ?21.23 and ?27.89 ‰, indicating that the source of the graphite was a primitive biogenic carbon material. High-grade metamorphic graphites show average temperatures around 729°C, while hydrothermal recrystallizated graphites (vein-graphites) show temperatures around 611°C by XRD, which correspond to granulite- to amphibolite facies conditions. The hydrothermal process with percolation of C-O-H fluids leads to a decrease in the crystal size along stacking direction (Lc₍₀₀₂₎) when compared with the previously formed high-grade metamorphism graphites. An update of the current tectonic model about the collisional process during Rhyacian-Orosirian orogeny in the Sao Francisco Craton is proposed to insert the formation of the Itapecerica graphite-rich metasedimentary sequence.     

江西铜坑嶂斑岩钼矿床成矿流体特征与成矿作用研究

江西铜坑嶂钼矿是新近发现的中型斑岩型钼矿,矿体主要分布在白垩纪花岗斑岩体内。根据矿物组合和穿插关系可将该矿床分为三个矿化蚀变阶段:钾硅酸盐化阶段、萤石-黑云母(白云母)-钾长石-辉钼矿阶段和绢云母-石英-碳酸盐阶段。流体包裹体研究表明早阶段成矿流体为富含碱质、挥发份的高氧化性岩浆流体,该成矿流体形成压力较大(约1000bar),温度较高(550～>600℃之间)并发生了沸腾作用,分离出高盐度多相流体包裹体和富气相低盐度包裹体。随着温度的降低(420～440℃之间)和压力的持续释放(320～360bar)成矿流体再次沸腾并导致了钼矿的沉淀。晚阶段与绢云母化等蚀变有关的脉体中大量存在的高盐度(29.58%～44.12%NaCleqv)流体包裹体指示岩浆流体为该蚀变作用的主导,该阶段少数石英脉中富液相包裹体的广泛发育可能与岩浆水和大气降水的混合作用有关。激光拉曼和扫描电镜实验在早阶段流体中检测到Fe3O4、SO2,表明该阶段流体氧化性较高,钾长石化发育,属碱性环境。主成矿阶段流体中还原性气体CH4等的存在,以及辉钼矿与蚀变白云母共生,揭示出该阶段处于相对还原的酸性环境,亦表明氧逸度、pH值变化可能共同导致了钼的沉淀。