矿物解理属性在宝石鉴定中的应用

解理面反光和光泽、解理的完全度、解理面组数及其夹角、解理的空间形态、解理面反光与矿物粒度的关系等构成了矿物解理的属性，这些属性在不同种的宝石矿物或同种宝石矿物各个体中性质不同，因此可应用于宝石的鉴定，尤其肉眼对翡翠鉴别时起到关键作用。     

费氏台测量解理的准确定位方法

本文介绍了用费氏台对解理直立定位测量的一种新操作方法,地提高解理水平定位的准确性提出了见解,并试图通过地传统解理定位操作的改进,提高费氏台测量解理的精度。     

响溪金矿区成矿地质特征与找矿方向分析

响溪金矿区周边出露黄茅园复式岩体、中华山岩体和其它隐伏岩体等,岩浆多期次活动。岩体与周边围岩金丰度值高,NE向张扭性断层贯穿岩体与围岩,围岩中发育NW向劈理化带是外接触带矿床的容矿构造。建议加强岩体及贯穿岩体的NE向断层的含矿性研究是寻找内接触带矿床的突破口,外接触带矿床主要需加强平行劈理化带的找矿,已知矿区要加强走向上的浅部控制。     

FOCAL MECHANISM SOLUTIONS AND STRESS FIELD OF THE 2019 CHANGNING,SICHUAN MAINSHOCK AND ITS MODERATE-STRONG AFTERSHOCKS(MS≥4.0)

A M_S6.0 earthquake with shallow focal depth of 16km struck Changning County, Yibin City, Sichuan Province at 22:55: 43(Beijing Time)on 17 June 2019. Although the magnitude of the earthquake is moderate, it caused heavy casualties and property losses to Changning County and its surrounding areas. In the following week, a series of aftershocks with M_S≥4.0 occurred in the epicentral area successively. In order to better understand and analyze the seismotectonic structure and generation mechanism of these earthquakes, in this paper, absolute earthquake location by HYPOINVERSE 2000 method is conducted to relocate the main shock of M_S6.0 in Changning using the seismic phase observation data provided by Sichuan Earthquake Administration, and focal mechanism solutions for Changning M_S6.0 main shock and M_S≥4.0 aftershocks are inferred using the gCAP method with the local and regional broadband station waveforms recorded by the regional seismic networks of Sichuan Province, Yunnan Province, Chongqing Municipality, and Guizhou Province. The absolute relocation results show that the epicenter of the main shock is located at 28.35°N, 104.88°E, and it occurred at an unusual shallow depth about only 6.98km, which could be one of the most significant reasons for the heavier damage in the Changning and adjoining areas. The focal plane solution of the Changning M_S6.0 earthquake indicates that the main shock occurred at a thrust fault with a left-lateral strike-slip component. The full moment tensor solution provided by gCAP shows that it contains a certain percentage of non-double couple components. After the occurrence of the main shock, a series of medium and strong aftershocks with M_S≥4.0 occurred continuously along the northwestern direction, the fault plane solutions for those aftershocks show mostly strike-slip and thrust fault-type. It is found that the mode of focal mechanism has an obvious characteristic of segmentation in space, which reflects the complexity of the dislocation process of the seismogenic fault. It also shows that the Changning earthquake sequences occurred in the shallow part of the upper crust. Combining with the results from the seismic sounding profile in Changning anticline, which is the main structure in the focal area, this study finds that the existence of several steep secondary faults in the core of Changning anticline is an important reason for the diversity of focal mechanism of aftershock sequences. The characteristics of regional stress field is estimated using the STRESSINVERSE method by the information of focal mechanism solutions from our study, and the results show that the Changning area is subject to a NEE oriented maximum principal stress field with a very shallow dipping and near-vertical minimum principal stress, which is not associated with the results derived from other stress indicators. Compared with the direction of the maximum principal compressive stress axis in the whole region, the direction of the stress field in the focal area rotates from the NWW direction to the NEE direction. The Changning M_S6.0 earthquake locates in the area with complex geological structure, where there are a large number of small staggered fault zones with unstable geological structure. Combining with the direction of aftershocks distribution in Changning area, we infer that the Changning M_S6.0 earthquake is generated by rupturing of the pre-existing fault in the Changning anticline under the action of the overall large stress field, and the seismogenic fault is a high dip-angle thrust fault with left-lateral strike-slip component, trending NW.     

Polyphase deformation and garnet growth in pelitic schists of Sausar Group in Ramtek area,Maharashtra, India: A study of porphyroblast-matrix relationship

Polyphase deformation and metamorphism of pelitic schists of Chorbaoli Formation of Sausar Group in and around Ramtek area, Nagpur district, Maharashtra, India has led to the development of garnet and sataurolite porphyroblasts in a predominantly quartz-mica matrix. Microstructural study of oriented thin sections of these rocks shows that garnet and staurolite have different growth histories and these porphyroblasts share a complex relationship with the matrix. Garnet shows at least two phases of growth — first intertectonic between D₁ and D₂ (pre-D₂ phase) and then syn-tectonic to post-tectonic with respect to D₂ deformation. Growth of later phase of garnet on the earlier (pre-D₂) garnet grains has led to the discordance of quartz inclusion trails between core and rim portion of the same garnet grain. Staurolite develops only syn-D₂ and shows close association with garnet of the later phase. The peak metamorphic temperature thus coincided with D₂ deformation, which developed the dominant crenulation schistosity (S₂), regionally persistent in the terrain. The metamorphic grade reached up to middle amphibolite facies in the study area, which is higher than the adjoining southern parts of Sausar Fold Belt.     

Testing models for the development of spiral-shaped inclusion trails in garnet porphyroblasts: to rotate or not to rotate, that is the question

Abstract The formation of spiral-shaped inclusion trails (SSITs) is problematical, and the two viable models for their formation involve opposite shear senses along the foliation in which the porphyroblasts are growing. One model argues for porphyroblast rotation, with respect to a geographically fixed reference frame, whereas the other argues for no such porphyroblast rotation, but instead rotation of the matrix foliation around the porphyroblast. Thus, porphyroblasts with SSITs cannot be used as shear-sense indicators until it is conclusively determined which model best explains them.
Any successful model must explain features associated with SSITs, including: (1) foliation truncation zones, (2) smoothly curving SSITs, (3) millipede microstructure, (4) total inclusion-trail curvature in median sections, (5) porphyroblasts with SSITs that have grown together, (6) evidence for relative porphyroblast displacements, (7) shear-sense indicators inside and outside porphyroblasts; (8) crenulations associated with porphyroblasts and (9) geometries in sections subparallel to spiral axes (axes of rotation). A detailed study of these features suggests that most, if not all, can be explained by both the rotational and non-rotational models, in spite of these models involving diametrically opposed movement senses. Therefore, geometrical analysis of individual porphyroblast microstructures may not determine which model best explains SSITs until the kinematics required to form these microstructures are better understood, in particular the sense of shear along a developing crenulation cleavage. Specific tests for determining the shear sense along crenulation cleavages are proposed, and results of such tests may conclusively resolve the debate over how SSITs form.     

Toxic Effects of Cadmium on Fertilizing Capability of Spermatozoa, Dynamics of the First Cleavage and Pluteus Formation in the Sea Urchin Anthocidaris crassispina (Agassiz)

Effects of cadmium on the fertilizing capability of spermatozoa, dynamics of the first cleavage and pluteus formation in the sea urchin, Anthocidaris crassispina, were investigated. Exposure to cadmium concentrations of 0.32, 0.56, 1.0, 1.8, 3.2, 5.6 and 10.0 mg l⁻¹ for 30 min caused a significant adverse effect on the fertilizing capability of spermatozoa (EC₅₀=1.7 mg l⁻¹). For the first cleavage kinetics assay, eggs were pre-exposed to 0, 0.18, 0.32, 0.56, 1.0, 1.8, 3.2 and 5.6 mg l⁻¹ of cadmium for 30 min. Fresh sperms of fixed concentrations were then added to the eggs and the percentage of divided zygotes estimated. Concentration-dependent toxic effects on the dynamics of the first cleavage in A. crassispina were observed between 0.18 and 5.6 mg l⁻¹ cadmium. Calculation of EC₅₀ values by probit analysis at different stages of the first cleavage revealed that EC₅₀ values increased gradually from 0.37 mg l⁻¹ at the beginning to 2.24 mg l⁻¹ at the end of the cleavage process. Different larval classes (normal, abnormal and retarded plutei, preplutei, dead embryos/larvae) of A. crassispina obtained from eggs pre-treated with cadmium for 30 min and then exposed to cadmium throughout embryogenesis were also examined. The percentage of abnormal plutei was significantly higher than that of the control at 0.56 mg l⁻¹ cadmium and higher. The 48 h EC₅₀ calculated for the number of normal plutei was 1.5 mg l⁻¹. A χ²-test revealed significant changes in the distribution of proportions of different larval classes only at cadmium concentrations 1.8 mg l⁻¹. At 5.6 mg l⁻¹ of cadmium, small malformed plutei, and oval embryos with rudimentary skeleton, poorly differentiated intestines and no mouth (pre-pluteus stage) were observed. The relative sensitivity of various end points to cadmium is also compared and discussed.     

共轭伸展褶劈理夹角的定量解析

通过静力和动力学解析,共轭伸展褶劈理面对最大主应力方向的理想夹角为１０９°２８′,与实际观测值一致。共轭伸展褶劈理的取向取决于形成时剪切作用类型,纯剪切时以糜棱面理为对称面,但在一般剪切时则与之不对称。同向褶劈理与糜棱面理间的夹角变化于－ ９°４４′～３５°１６′之间,取决于简单剪切与纯剪切的相对组分。共轭两组常不同等发育。Ｐ方向的同向剪切趋势抑制反向褶劈理的形成。同向伸展褶劈理的扩展是导致低角正断层形成的有效机制     

大青山逆冲推覆构造带中劈理特征及其成因

在大青山逆冲推覆构造带中发育一组非透入性板劈理构造,主要发育有两种劈理,分布在中部构造岩片和外缘构造带中。第一种劈理分布在主干逆冲断层下盘,受断层控制,为一组压扭性构造面,其产状、变形特征和滑动方向与主干逆冲断层相一致;第二种劈理为层间劈理,受岩性控制。沿着劈理面同构造新生矿物组合和碎屑颗粒变形特征表明,劈理形成于地壳中浅部构造层次上的低绿片岩相条件下,以韧脆性变形机制为主。劈理切割了大青山褶皱构造,形成时代为(121.6±1.6) Ma。应力场的分析表明,劈理构造由近南北向的地壳水平挤压应力作用形成。     

弱片理化石英砂岩构造微区特征

采自韧性剪切带外侧的弱片理化石英砂岩不同构造微区特征,显示岩石的片理化受到多方面因素的制约和影响,如岩石中砂粒的含量和砂粒的粒度。片理化过程砂粒有旋转和拉伸变形,粒度较小的颗粒优先旋转并有较大的拉伸应变量,颗粒粒度敏感变形机制是该岩石的主要变形机制。