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   

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   

宿松变质杂岩中石榴石-蓝晶石-硬绿泥石片岩形成条件及时限研究     

石永红  王娟  聂峰  曹晟  康涛 《岩石学报》2016,32(2):493-504

宿松变质杂岩因变质程度较低,岩性较为繁杂,故其变质演化及年龄一直缺乏系统性和全面性研究,这很大程度上影响了人们对大别造山带结构框架和演化的深入理解。本次研究主要针对太湖-马庙断裂和柳林-缺月岭-山龙断裂之间的宿松变质杂岩进行了综合细致的分析,确定了特征性的高压岩石——石榴石-蓝晶石-硬绿泥石片岩的存在。利用THERMOCALC的Average P-T法,确定了石榴石-蓝晶石-硬绿泥石片岩的峰期变质温压条件为T=551~569℃和P=1.96~2.47GPa,属于高压榴辉岩相。LA-ICP-MS锆石U-Pb定年显示该岩石的峰期变质年龄为242.2±2.0Ma,退变质年龄为216.2±6.6Ma。结合区域地质调查和前人的研究成果,该岩石可能普遍存在于这两断裂之间,并暗示了这两断裂之间的块体经历了高压变质作用,其应当从宿松变质杂岩中剥离出来。本文在此暂定名为大山-麻石沟高压块体,并建议宿松变质杂岩的北界止于柳林-缺月岭-山龙断裂。  相似文献   

An investigation into the relationship between salt weathering debris production and temperature     

Alan Paul Davison 《地球表面变化过程与地形》1986,11(3):335-341

An investigation using laboratory simulation has been made using air temperature data for Tunisia, Antarctica, and southwest England. An experiment with a 50 cycle run produced results which showed significantly greater debris production in the Antarctica and Tunisian simulations than in the southwest England simulation. Using X-ray analysts to determine salt penetration, an inverse relationship between salt penetration and debris production was seen to exist. This could be the result of evaporation in the Tunisian simulation and rapid freezing in the Antarctic simulation, concentrating salts in the upper layers of the rock samples. In the southwest England simulation, no freezing, and relatively high humidities allowed greater penetration, thus distributing an equal input of salt over a greater area. The author tentatively suggests the possible existence of a parabolic relationship between salt weathering and temperature.  相似文献   

Dynamic melting of the Precambrian mantle: evidence from rare earth elements of the amphibolites from the Nellore–Khammam Schist Belt, South India     

K. Vijaya Kumar  M. Narsimha Reddy  C. Leelanandam 《Contributions to Mineralogy and Petrology》2006,152(2):243-256

The Nellore–Khammam Schist Belt (NKSB) in South India is a Precambrian greenstone belt sited between the Eastern Ghats Mobile Belt (EGMB) to the east and the Cratonic region to the west. The belt contains amphibolites, granite gneisses and metasediments including banded iron formations. Amphibolites occurring as dykes, sills and lenses—in and around an Archaean layered complex—form the focus of the present study. The amphibolites are tholeiitic in composition and are compositionally similar to Fe-rich mafic rocks of greenstone belts elsewhere. The NKSB tholeiites show highly variable incompatible trace element abundances for similar Mg#s, relatively constant compatible element concentrations, and uniform incompatible element ratios. Chondrite-normalized REE patterns of the tholeiites range from strongly LREE depleted ((La/Yb) _N = 0.19) to LREE enriched ((La/Yb) _N = 6.95). Constant (La/Ce) _N ratios but variable (La/Yb) _N values are characteristic geochemical traits of the tholeiites; the latter has resulted in crossing REE patterns especially at the HREE segment. Even for the most LREE depleted samples, the (La/Ce) _N ratios are > 1 and are similar to those of the LREE enriched samples. There is a systematic decrease in FeO^t, K₂O and P₂O₅, as well as Ce and other incompatible elements from the LREE enriched to the depleted samples without any variation in the incompatible element ratios and Mg#s. Neither batch and fractional melting, nor magma chamber processes can account for the non-correlation between the LREE enrichment and HREE concentrations. We suggest that dynamic melting of the upper mantle is responsible for these geochemical peculiarities of the NKSB tholeiites. Polybaric dynamic melting within a single mantle column with variable mineralogy is the likely mechanism for the derivation of NKSB tholeiitic melts. It is possible that the NKSB tholeiites are derived from a source with higher FeO/MgO than that of present day ridge basalts.  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   

中亚造山带东段西拉木伦构造带的性质与演化：来自变形和低温热年代学的约束          下载免费PDF全文

张进  曲军峰  刘建峰  王艳楠  赵衡  赵硕  张北航  郑荣国  云龙  杨亚琦  牛鹏飞 《沉积与特提斯地质》2021,41(2):190-217

中亚造山带东段何时与何地关闭,从俯冲到关闭的过程以及随后的陆内演化又经历了什么主要事件,目前还存在不同认识。中亚造山带东段林西地区的蛇绿混杂岩及其周围地区的区域地质调查表明,以杏树洼蛇绿混杂岩和双井片岩为代表的西拉木伦河构造带是一个晚古生代的增生楔,在该混杂岩带中发育了典型的岩块被包裹在基质中的构造。该楔体被中、晚二叠世克德河砾岩所覆盖。增生楔中最早的近东西向构造代表了向南俯冲阶段的变形,随后继续经历向北的逆冲推覆,卷入了中、晚二叠世地层,形成了碰撞期的变形;在晚二叠世末期—三叠纪早期,蛇绿混杂岩以及上覆的克德河砾岩又经历了区域性的强烈的右行韧性剪切,并发生应变分解。晚二叠世区域性的右行韧性剪切在中亚造山带南缘普遍发育,代表了中亚造山带已经全部进入陆内环境。双井片岩也经历了与蛇绿混杂岩类似的变形事件,在增生楔下部经历变质作用,并在碰撞期抬升至地表,晚期为区域性的右行剪切。同时,结合锆石与磷灰石低温热年代学测试表明,双井片岩和蛇绿混杂岩共同经历了中、晚侏罗世源自北侧蒙古-阿霍茨克大洋关闭导致的近南北向挤压、早白垩世期间遍及东亚的区域性伸展以及晚白垩世短暂的构造反转事件。  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   

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   

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