遥感岩性识别研究的发展趋势--遥感与航空放射性信息集成   总被引：5，自引：0，他引：5  

张万良 《矿物岩石地球化学通报》2005,24(1):88-91

岩石的吸收光谱主要是由杂质、包体、蚀变及替代成分产生的,每种岩石都难以形成象它的组成成分那样具有可分辨的很清晰的光谱特征;不同类型的岩石放射性元素的含量和分布特征是不同的,岩石放射性信息是岩性识别研究的重要判据。遥感与航空放射性信息的集成．既能提取光谱图像中的光语信息和空间纹理信息。又可利用航空放射性信息常常具有的甚至是诊断性的岩性识别能谱标志。能明显提高识别岩性的精度,更重要的是能谱不受值被的影响,有利于识别植被覆盖区的岩性。因此,这可能是遥感岩性识别研究的发展趋势之一。  相似文献   

峨眉山大火成岩省中的苦橄岩:地幔柱活动证据   总被引：9，自引：0，他引：9  

张招崇  王福生  郝艳丽 《矿物岩石地球化学通报》2005,24(1):17-22

峨眉山大陆溢流玄武岩省中新发现的苦橄质熔岩中的橄榄石和铬尖晶石分别以富镁和富铬为特征。利用橄榄石熔体平衡原理恢复得到原生岩浆的MgO含量约为22％．表明该地区既有代表原生岩浆成分的苦橄岩,也有代表演化和堆晶成因的苦橄岩,根据有关实验估算其形成的T=1600℃,p=4．5GPa。如此高的温度指示了苦橄岩的形成与地幔柱作用有关。其稀土和微量元素配分模式以轻稀土富集和高场强元素(HFSE)相对亏损．不存在Nb、Ta负异常,而以P和K负异常为特征。其La／Ta、La／Sm、(La／Nb)PM、(Th／Ta)PM值变化范围小,均指示其地幔柱成因,且上升过程中很少或没有受到岩石圈地幔或地壳物质的混染,是石榴二辉橄榄岩经大约7％的部分熔融的产物。地幔柱的轴部位置可能位于现今云南丽江县城一带。  相似文献   

东海E1孔晚更新世以来的地层、生物与环境   总被引：6，自引：0，他引：6       下载免费PDF全文

张静林景星  剧远景李双林李绍全  王绍芳许波 《地质学报》2004,78(1):9-16

东海E1孔水深100m，是迄今东海陆架水深最深、采样最密、研究最详细的钻孔。依据有孔虫动物群的研究和碳同位素测年，可将E1孔的地层分成3段：S1—S3(0．00～3．34m)为全新统；S4—S24(3．34～53．43m)为晚更新统；S25(53．43～55．63m)为中更新统。有孔虫以浮游种类为主，属热带至亚热带动物群。研究发现本区自晚更新世以来有3次高海面期：第一次高海面期与长江三角洲平原的镇江海进、华北平原的天津海进和华南的长乐海进相当，属全新世，为外浅海环境；第二次高海面期与长江三角洲平原的隔湖海进、华北平原的沧州海进、和华南的福州海进相当，属晚更新世晚期，为外浅海环境；第三次高海面期与长江三角洲的江阴海进、华北平原的白洋淀海进相当，属晚更新世早期，为中至外浅海环境。在最晚中更新世低海面期本区曾暴露成陆。  相似文献   

A TEM study of exsolution in Ca-rich pyroxenes from the Paris and Renazzo chondrites: Determination of type I chondrule cooling rates     

Priscille Cuvillier  Noël Chaumard  Hugues Leroux  Brigitte Zanda  Roger H. Hewins  Damien Jacob  Bertrand Devouard 《Meteoritics & planetary science》2018,53(3):482-492

We conducted a transmission electron microscope study of the exsolution microstructures of Ca-rich pyroxenes in type I chondrules from the Paris CM and Renazzo CR carbonaceous chondrites in order to provide better constraints on the cooling history of type I chondrules. Our study shows a high variability of composition in the augite grains at a submicrometer scale, reflecting nonequilibrium crystallization. The microstructure is closely related to the local composition and is thus variable inside augite grains. For compositions inside the pyroxene miscibility gap, with a wollastonite (Wo) content typically below 40 mole%, the augite grains contain abundant exsolution lamellae on (001). For grain areas with composition close to Wo₄₀, a modulated texture on (100) and (001) is the dominant microstructure, while areas with compositions higher than Wo₄₀ do not show any exsolution microstructure development. To estimate the cooling rate, we used the spacing of the exsolution lamellae on (001), for which the growth is diffusion controlled and thus sensitive to the cooling rate. Despite the relatively homogeneous microstructures of augite grains with Wo < 35 mole%, our study of four chondrules suggests a range of cooling rates from ~10 to ~1000 °C h⁻¹, within the temperature interval 1200–1350 °C. These cooling rates are comparable to those of type II chondrules, i.e., 1–1000 °C h⁻¹. We conclude that the formation of type I and II chondrules in the proto-solar nebula was the result of a common mechanism.  相似文献   

Cooling rates of type I chondrules from Renazzo: Implications for chondrule formation     

Noël Chaumard  Munir Humayun  Brigitte Zanda  Roger H. Hewins 《Meteoritics & planetary science》2018,53(5):984-1005

Cooling rates are one of the few fundamental constraints on models of chondrule formation. In this study, we used Cu and Ga diffusion profiles in metal grains to determine the cooling rates of type I chondrules in the Renazzo CR2 chondrite. To improve previous estimations of cooling rates obtained using this method, we used CT scanning and serial polishing of our sections to analyze equatorial sections of large metal grains. Through the cores of these metal grains situated at the surface of chondrules, the cooling rates calculated range from 21 to 86 K h⁻¹ for a peak temperature T_p ~ 1623–1673 K. A metal grain embedded in the core of a chondrule exhibits a cooling rate of 1.2 K h⁻¹ at a T_p ~ 1573 K. We also measured Cu-Ga diffusion profiles from nonequatorial sections of metal grains and calculated a lower range of cooling rates of 15–69 K h⁻¹ for T_p ~ 1473–1603 K compared to our results from equatorial sections. The high cooling rates inferred from the lightning model (several thousand K h⁻¹) are clearly at odds with the values obtained in this work. The X-wind model predicts cooling rates (~6–10 K h⁻¹) lower than most of our results. The cooling rates calculated here are in close agreement with those inferred from shock wave models, in particular for temperatures at which olivine crystallizes (from ~10 to several hundreds K h⁻¹ between 1900 and 1500 K). However, the chemical compositions of metal grains in Renazzo are consistent with the splashing model, in which a spray of metal droplets originated from a partially molten planetesimal. Volatile siderophile element depletion is explained by evaporation before metal was engulfed within silicate droplets. Liquid metal isolated from the liquid silicate crystallized during cooling, reacted with the ambient gas, and then re-accreted within partially molten chondrules.  相似文献   

Geochemistry of Apatite from the Apatite-rich Iron Deposits in the Ningwu Region, East Central China     

YU Jinjie ZHANG Qi MAO Jingwen YAN Shenghao 《《地质学报》英文版》2007,81(4):637-648

Four types of apatite have been identified in the Ningwu region.The first type of apatite is widely distributed in the middle dark colored zones(i.e.iron ores) of individual deposits.The assemblage includes magnetite,apatite and actinolite(or diopside).The second type occurs within magnetite-apatite veins in the iron ores.The third type is seen in magnetite-apatite veins and (or) nodules in host rocks(i.e.gabbro-diorite porphyry or gabbro-diorite or pyroxene diorite).The fourth type occurs within apatite-pyrite-quartz veins filling fractures in the Xiangshan Group.Rare earth elements (REE) geochemistry of apatite of the four occurrences in porphyry iron deposits is presented.The REE distribution patterns of apatite are generally similar to those of apatites in the Kiruna-type iron ores,nelsonites.They are enriched in light REE,with pronounced negative Eu anomalies.The similarity of REE distribution patterns in apatites from various deposits in different locations in the world indicates a common process of formation for various ore types,e.g. immiscibility.Early magmatic apatites contain 3031.48-12080×10~(-6) REE.Later hydrothermal apatite contains 1958×10~(-6) REE,indicating that the later hydrothermal ore-forming solution contains lower REE.Although gabbro-diorite porphyry and apatite show similar REE patterns,gabbro-diorite porphyries have no europium anomalies or feeble positive or feeble negative europium anomalies, caused both by reduction environment of mantle source region and by fractionation and crystallization(immiscibility) under a high oxygen fugacity condition.Negative Eu anomalies of apatites were formed possibly due to acquisition of Eu~(2+) by earlier diopsite during ore magma cooling. The apatites in the Aoshan and Taishan iron deposits yield a narrow variation range of ~(87)Sr/~(86)Sr values from 0.7071 to 0.7073,similar to those of the volcanic and subvolcanic rocks,indicating that apatites were formed by liquid immiscibility and differentiation of intermediate and basic magmas.  相似文献   

南岭东段赣南地区天门山花岗岩体及花岗斑岩脉的SHRIMP定年及其意义   总被引：16，自引：5，他引：11  

刘善宝王登红  陈毓川许建祥曾载林  应立娟王成辉 《地质学报》2007,81(7):972-978

赣南地区岩浆岩分布广泛,其中燕山期岩浆活动最为强烈,与W、Sn、Nb、Ta成矿的关系尤为密切。选择天门山岩体及附近的花岗斑岩脉为研究对象,应用SHRIMP锆石微区U-Pb测年技术,对天门山岩体的主体、补体和花岗斑岩脉进行了精确测年:天门山岩体的主体——中细粒斑状黑云母花岗岩锆石的9个点SHRIMP谐和年龄为152±2Ma(MSWD=1.09);补体——细粒斑状黑云母花岗岩锆石的5个点SHRIMP谐和年龄为152±2.6Ma(MSWD=0.16);花岗斑岩(墙)脉锆石10个点的SHRIMP谐和年龄为150.8±1.8Ma(MSWD=1.6)。结合区域资料,研究表明:①天门山岩体的主体形成于中侏罗世,补体是主体进一步分异演化的产物;②在赣南西部的崇余犹矿集区内成岩与成矿的年龄基本上是协调一致的,成矿集中期为150~155Ma;③岩浆活动由中深成相花岗岩侵入体演化到浅成相花岗斑岩脉仅相差1~5Ma,表明存在成矿集中期。  相似文献   

新疆玛因鄂博断裂带中花岗质糜棱岩锆石U-Pb SHRIMP和黑云母40Ar-39Ar年龄及意义   总被引：14，自引：0，他引：14  

周刚  张招崇  王新昆  王祥  罗世宾  何斌  张小林 《地质学报》2007,81(3):358-369

玛因鄂博断裂带具有左型剪切活动特征,分布其中的花岗质糜棱岩呈脉状、条带状产出,展布方向与剪切拉伸方向一致,为同构造花岗岩。其岩石化学为高钾钙碱性系列,属后碰撞“I”型花岗岩;稀土元素含量较高,ΣREE为(239.14~266.31)×10-6;具有中等程度的铕负异常,δEu为0.45~0.66,轻稀土明显富集。其锆石U-PbSHRIMP年龄为281±4Ma,黑云母40Ar-39Ar等时线年龄为236.1±1.2Ma。二者分别代表岩石的侵入年龄和后期的剪切变形年龄。其形成与早二叠世区域性大规模剪切活动有关,而黑云母40Ar-39Ar等时线年龄代表中三叠世早期的剪切变形活动。结合前人资料分析,玛因鄂博断裂的剪切活动持续时间较长,高峰期可能为290~270Ma,而其最后结束时间为230Ma左右。  相似文献   

~(40)Ar/~(39)Ar Thermochronological Constraints on the Timingof Collisional Orogeny in the Mian-Lite Collision Belt,Southern Qinling Mountains     

LI Jinyi  WANG Zongqi  ZHAO Min Institute of Geology  Chinese Academy of Geological Sciences  Beijing 《《地质学报》英文版》1999,73(2)

Silurian, Devonian and Carboniferous geological bodies in the Mianxian-Lueyang (Mian-Lue) collisional belt (MLB) and its neighbouring areas, southern Qinling Mountains, China, show similar characteristics of having undergone deformation of two stages. The earlier one, which is inferred to be related to collisional orogeny between the Yangtze and Sino-Korean palaeocontinents based on previous geological data, is responsible for large-scale, north-verging recumbent folds and overthrusts, and associated with low greenschist fades metamorphism. 40Ar/39Ar dating of three muscovite samples taken from different localities yields plateau ages of 226.9±0.9 and 219.5±1.4 Ma and an apparent age of 194.5±3.0 Ma. Thus, the late Triassic collision between the Yangtze and Sino-Korean palaeocontinents has been constrained.  相似文献   

Characteristics of Upper Mantle Activity in the South China Sea Region and the Indochina Mantle Plume   总被引：2，自引：0，他引：2  

WU Nengyou  ZENG Weijun  LI Zhenwu  CHEN Yizhong  WEN Xiwen  DU Deli  LI Guosheng Guangzhou Marine Geological Survey  MGMR  PO Box  Guangzhou 《《地质学报》英文版》1999,73(4):464-476

According to computed results of the mantle traction field beneath the lithosphere based on satellite-modelled gravity anomalies of different degrees, it has been revealed that the three types of mantle convection on different scales existing in the South China Sea region is the key factor controlling the geodynamics. The mantle convection models on large and middle scales have been proved by natural seismic S-wave tomographic data and interpreted by using the present mantle plume concept In consideration of other relevant geological and geophysical data, the authors put emphasis on discussing the expression form, origin and age of the Indochina mantle plume and its important effect on the conversion of organic matter and hydrocarbon accumulation in Cenozoic basins.  相似文献