福建屏南黛溪铅锌矿床地质特征与成因   总被引：3，自引：0，他引：3  

马春 《福建地质》2002,21(1):21-26

福建屏南黛溪铅锌矿床形成了火山活动频繁的断陷带中，矿体产于火山基底“构造窗”震旦纪龙北溪组地层中，矿化受绿片岩相控制，矿体呈似层状，与围岩产状一致，矿石具特殊的结构和构造，矿物组分简单，品位低，规模较大，硫主要来源于花岗质岩浆，铅来源于地壳，有陆源铅混染，表现为“层控型”矿床特征和多期次地质作用的叠加改造。  相似文献   

木兰山蓝片岩中斜黝帘石—低铁绿帘石连生体的确定   总被引：1，自引：1，他引：1  

赵文俞  牟善斌等 《岩矿测试》2002,21(1):29-32

电子探针和光学显微镜联合分析表明，木兰山蓝片岩中存在斜黝帘石－低铁绿帘石连生体。界面区Fe、Al元素的线扫描曲线研究表明，（Fe,Al)类质同象替代为连生体界面共晶膜的形成机制。木兰山蓝片岩中斜黝帘石－低铁绿帘石连生体的确定，说明电子探针和光学显微镜联合分析可有效确定光学性质和化学成分均相近的微细粒连生体的组成矿物，其结果对认识木兰山蓝片岩的变质演化具有指示意义。  相似文献   

Mechanism of creep movement caused by landslide activity and underground erosion in crystalline schist, Shikoku Island, southwestern Japan   总被引：12，自引：0，他引：12  

G. Furuya  K. Sassa  H. Hiura  H. Fukuoka 《Engineering Geology》1999,53(3-4):311-325

The mechanism of creep movement of the Zentoku landslide in crystalline schist has not been studied in detail because of the steepness of the slope, very slow movement, low population density and complex topographic and geologic characteristics. Sassa et al. (1980: Proc. INTERPRAEVENT 1, 85–106) and Sassa (1984: Proc. 4th International Symp. on Landslides, Toronto, vol. 2, pp. 179–184; 1985. Geotechnical classification of landslides, Proc. 4th International Conference and Field Workshop on Landslides, Tokyo, pp. 31–40; 1989: Landslide News, Japan Landslide Society, No. 3, pp. 21–24) monitored landslide movement and groundwater level at the Zentoku landslide on Shikoku Island, southwestern Japan, and suggested that the mechanism may be caused by underground erosion. To study the influence of underground erosion at this site, continual monitoring of suspended sediment and water discharge from a groundwater outlet (i.e. a spring) was implemented. The locations of groundwater flow paths were determined, as were the amounts of discharged sediment. Slope deformation was monitored by means of a borehole inclinometer. The conclusions were as follows: (1) the flow paths were found to be on or above the shear zones in which underground erosion has occurred; (2) in addition to being a result of precipitation and groundwater discharge, sediment discharge is affected by landslide activity; and (3) the mechanism of creep movement is an interrelated chain process that combines underground erosion caused by landslide activity with landslide activity caused by underground erosion. Thus, landslide activity increases erosion susceptibility and transportation of soils within the mass, and underground erosion causes instability of the landslide mass, in turn.

This mechanism can explain the observed phenomenon that the Zentoku landslide not only moves actively during heavy rain, but also continues to creep throughout the year.  相似文献   

Early Cretaceous tectonic events implied in the time-lag between the age of radiolarian chert and its metamorphic basement in the Bantimala area, South Sulawesi, Indonesia     

Koji  Wakita  Munasri  Jan  Sopaheluwakan  Iskandar  Zulkarnain Kazuhiro  Mlyazaki 《Island Arc》1994,3(2):90-102

Abstract The Bantimala Complex of South Sulawesi consists mainly of mélange, chert, basalt, ultramafic rocks and high pressure type metamorphic rocks. Well-preserved radiolarians were extracted from 10 samples of chert, and K-Ar age dating was done for muscovite from five samples of schist of the Bantimala Complex. The radiolarian assemblage from chert is assigned middle Cretaceous (late Albian-early Cenomanian) age, while the K-Ar age data from schist range from 132 Ma to 114 Ma except for one sample with rare muscovite. The radiolarian chert is unconformably underlain by schist in the Bantimala Complex. The stratigraphie relationship and the time lag of these two kinds of age data from chert and underlying schist suggest short-time tectonic events immediately followed by a quick waning tectonism in this region during the Albian-Cenomanian transgression.  相似文献   

Talc-phengite-albite assemblage in piemontite-quartz schist of the Sanbagawa metamorphic belt, central Shikoku, Japan     

J. Izadyar  T. Hirajima†  D. Nakamura‡ 《Island Arc》2000,9(1):145-158

Abstract The talc (Tlc) + phengite (Phn) + albite (Ab) assemblage is newly confirmed in MnO^total-rich (1.65 wt% in average) piemontite-quartz schists from the intermediate- and high-grade part of the Sanbagawa belt, central Shikoku, Japan. Talc is in direct contact with Phn, Ab and chlorite (Chl) with sharp boundaries, suggesting that these four phases mutually coexist. Other primary constituents of the Tlc-bearing piemontite-quartz schist are spessartine, braunite, hematite (Ht), crossite/barroisite and dolomite. Phlogopite (Phl) rarely occurs as a later stage mineral developing along the rim of Phn. The studied piemontite-quartz schist has mg# (= Mg/(Mg + Fe²⁺)) ~ 1.0, because of its high oxidation state. Schreinemakers' analysis in the KNMASH system and the mineral assemblage in the Sanbagawa belt propose a possible petrogenetic grid, in which the Tlc–Phn assemblage is stable in a P-T field surrounded by the following reactions: lower-pressure limit by Chl + Phl + quartz (Qtz) = Phn + Tlc + H₂O as proposed by previous workers; higher-pressure limit by glaucophane + Qtz = Tlc + Ab + H₂O; and higher-temperature limit by Tlc + Phn + Ab = Phl + paragonite + Qtz + H₂O. Thermodynamic calculation based on the database of Holland & Powell (1998) , however, suggests that the Tlc–Phn stability field defined by these reactions is unrealistically limited around 580–600 °C at 11.6–12.0 (± 0.7) kbar. Schreinemakers' analysis in the KNMA-Fe³⁺-SH system and the observed mineral assemblage predict that Chl + crossite = Tlc + Ab + Ht + H₂O is a preferable Tlc-forming reaction in the intermediate-grade part of the Sanbagawa belt and that excess Ab + hematite narrows the stability field of the Tlc–Phn assemblage.  相似文献   

颗粒破碎对绢云母片岩强度和变形影响的试验研究     

秦尚林  杨兰强  陈荣辉  陈善雄 《岩土力学》2014,35(11):3086-3092

为进一步弄清颗粒破碎对软岩粗粒料强度、变形的影响,开展2组不同初始干密度下的绢云母片岩粗粒料的固结排水三轴试验,分析了绢云母片岩粗粒料颗粒破碎规律,并探讨了颗粒破碎对绢云母片岩粗粒料力学性质的影响。结果表明,绢云母片岩粗粒料相对破碎率随围压的增加而增大,但颗粒破碎增幅速率受初始干密度影响较大,颗粒破碎与围压之间的关系可用线性关系描述;由于初始孔隙率的影响,使得试样在同一应力水平下高密度试样颗粒破碎明显高于低密度试样;颗粒破碎对高密度试样抗剪强度降低的影响高于低密度试样,导致两种干密度试样的应力-应变曲线在某处出现相交,最终出现初始密度低的试样抗剪强度大于初始密度高的试样抗剪强度的现象;高密度试样孔隙率较小,其剪胀因子一直保持在1附近,而低密度试样孔隙率较大,受颗粒破碎和剪胀的影响迟缓一些,低密度试样体变较高密度要大些,但整体上由于颗粒破碎和剪胀的影响,绢云母片岩粗粒料的体变均不大。  相似文献   

藏东同卡石榴辉石岩和拉萨地体松多蓝片岩   总被引：3，自引：0，他引：3       下载免费PDF全文

沙绍礼谢尧武陈应明西洛朗杰刘学龙  张娜 蒋成兴 《中国地质》2009,36(6):1302-1311

元古宇卡穷岩群位于班公湖-怒江缝合带内,岩性为黑云斜长片麻岩、黑云斜长变粒岩,花岗片麻岩、大理岩及斜长角闪岩.黑云斜长片麻岩中具铁铝榴石、矽线石、蓝晶石组合.锆石U-Pb同位素年龄为1334 Ma,花岗片麻岩锆石U-Pb年龄(507±10)Ma(SHRIMP),后者可能属稍晚期变形变质的花岗岩侵入体.卡穷岩群属冈瓦纳大陆北缘裂离出来的微陆块.黑云斜长片麻岩中首次发现石榴辉石岩、榴闪岩包体.较新鲜的石榴辉石岩由角闪石、透辉石、石榴石及少量石英、金红石组成,无长石.包体岩石化学成分中SiO_248.65%～51.18%,K_2O＜1%,稀土配分形式为平坦型,无明显的Eu异常.微量元素Rb、Ba、Th富集,低Sr,具洋脊玄武岩特征.石榴石端元组分中铁铝榴石51.44%、镁铝榴石26.73%、钙铝榴石17.29%.透辉石端元组分中,硬玉分子平均为6.40%.镜下常见石榴石、辉石退变为角闪石和斜长石,包体岩石应为榴辉岩退变的产物.  相似文献   

P-T evolution of metapelites from the Bajgan complex in the Makran accretionary prism,south eastern Iran     

《Chemie der Erde / Geochemistry》2017,77(3):459-475

The Bajgan Complex, one of the basement constituents of the arc massif in Iranian Makran forms a rugged, deeply incised terrain. The complex consists of pelitic schists with minor psammitic and basic schists, calc silicate rocks, amphibolites, marbles, metavolcanosediments, mafic and felsic intrusives as well as ultramafic rocks. Metapelitic rocks show an amphibolite facies regional metamorphism and contain garnet, biotite, white mica, quartz, albite ± rutile ± apatite. Thermobarometry of garnet schist yields pressure of more than 9 kbar and temperatures between 560 and 675 °C. The geothermal gradient obtained for the peak of regional metamorphism is 19 °C/km, corresponding to a depth of ca. 31 km. Replacement of garnet by chlorite and epidote suggest greenschist facies metamorphism due to a decrease in temperature and pressure through exhumation and retrograde metamorphism (370–450 °C and 3–6 kbar). The metapelitic rocks followed a ‘clockwise’ P–T path during metamorphism, consistent with thermal decline following tectonic thickening. The formation of medium-pressure metamorphic rocks is related to presence of active subduction of the Neotethys Oceanic lithosphere beneath Eurasia in the Makran.  相似文献   

各向异性片岩的微观组构信息定量提取与断面形貌特征分析     

尹晓萌  晏鄂川  王鲁男  陈利 《岩土力学》2019,(7):2617-2627,2729

取3类具有明显片理面的武当群片岩,采用偏光显微镜、扫描电镜研究其微观组构、断面形貌特征。构建了面积百分比、尺寸与周长-面积分形维数、定向分布系数等指标,利用IPP专业图像处理软件,对矿物和孔隙(微裂隙)两系统的含量、形态、分布特征等进行定量分析;并基于Matlab的数字图像处理技术,对断裂面粗糙度展开定量评价。偏光显微镜下显示,片岩具有矿物定向排列与粒、片状矿物近互层状分布的典型特征。矿物系统的微观定量分析结果表明:武当群片岩白云母的含量为11%~30%;小岛法计算的白云母矿物周长-面积分形维数为1.31~1.39;定向分布系数为0.61~0.85;微裂隙依附于白云母矿物边缘孕育、扩展,导致武当群片岩的孔隙(微裂隙)微观指标与对应的矿物微观指标有较强的相关性。沿片理面的片岩断面主要呈现沿晶破坏特征,断口较平坦,基于断面形貌图绘制的灰度信号波曲线的盒维数为1.48~1.60;斜交片理面破裂的片岩断面以穿晶破坏为主,有穿晶-沿晶破坏交替而生的迹象,断口粗糙起伏,对应的灰度信号波曲线的盒维数为1.65~1.69。武当群片岩的断面粗糙度各向异性约为1.03~1.14。  相似文献   

石鼓-黎明地区变沉积岩系的深熔时代和物源     

王舫  刘福来  刘平华  蔡佳  施建荣  冀磊  刘利双 《岩石矿物学杂志》2019,38(6):881-896

以出露于石鼓-黎明地区的黑云母石英片岩及其深熔脉体为重点研究对象,对其中的锆石进行了阴极发光图像分析、SHRIMP和LA-ICP-MS U-Pb年代学研究。阴极发光图像显示,黑云母石英片岩中大部分锆石保留清晰的振荡环带;深熔脉体中大部分锆石具有核-边结构,核部保留清晰的振荡环带或呈灰色无分带结构,边部较窄呈黑色。对黑云母石英片岩及其深熔脉体中锆石核部进行定年,得到年龄范围为2 637～743 Ma,具有858～852 Ma的主要年龄峰值,表明其主要物质来源为扬子板块西缘新元古代岩浆岩,同时也有太古代-古元古代基底岩石的加入,沉积时代应晚于852 Ma。深熔脉体锆石边部的Th/U值较小(0. 1),得到206Pb/238U年龄变化于225～197 Ma之间,可能代表了变沉积岩的变质-深熔时代,该年龄与金沙江-点苍山-哀牢山变质带二叠纪-三叠纪变质事件的时代相一致。  相似文献