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151.
吉林省安图县海沟金矿床控矿构造特征 总被引:2,自引:0,他引:2
海沟金矿是大型石英贫硫化物脉型金矿床。矿区侵入岩可划分为四个花岗岩单元,矿体(脉)在平、剖面上都具有斜列的特点。含金石英脉的产出和分布严格受NNE-NE向断裂控制。金矿区控矿构造型式为EW向大断裂的派生断裂控制矿床,成矿构造序列划分为成矿前、成矿期、成矿后构造。构造对矿床(矿体)的控制作用主要表现为等距性构造控制矿脉分布;断裂多期活动对富矿体的控制。分析了断裂构造地球化学特征,表明成矿作用是以充填 相似文献
152.
中国东北区二叠纪和早三叠世地层 总被引:4,自引:1,他引:4
本文运用裂陷槽理论,提出了早二叠世地层发育于大石寨、大河深和庙岭三个裂陷槽中。晚二叠一早三叠世则以陆相凹陷沉积为特征,发育于兴安岭、张广才岭及完这山三个凹陷内。 相似文献
153.
陕西南部北大巴山地区早志留世滔河口组碱基性火山岩,分布层位稳定,岩性标志特征。根据火山岩岩石类型和地层学以及古生物组合特征对其岩石地层单位重新进行了厘定,研究了火山岩的成因,探讨了火山岩形成的机制和构造环境。 相似文献
154.
中国兴蒙—新疆北部及邻区早石炭世地层十分发育,动植物化石丰富。根据生物群综合分析,将该研究区归入哈萨克斯坦—西伯利亚域和特提斯域,并进一步划分为3个省,8个亚省。西伯利业省以管孔贝大量发育为特征,缺少大长身贝类,珊瑚不甚发育,植物少见,为安加拉植物群;哈萨克斯坦—蒙古—兴安省以管孔贝类和大长身贝类共同发育为突出特征,珊瑚较发育,但分区特征不明显,并有大量异珊瑚类,植物为安加拉植物群;塔里木北缘—西秦岭省以南方型生物群大量发育为主要特征,大长身贝类最为发育,缺少管孔贝类,珊瑚数量十分丰富,并有假乌拉珊瑚大量发育,植物以华夏植物群为主。早石炭世古生物地理分区与板块关系密切,晚泥盆世末,西伯利亚板块南移,与哈萨克斯坦板块汇聚,到早石炭世早、中期,两大板块基本上处于相近似的古生物地理环境,与此同时,塔里木板块逐渐北移,与哈萨克斯坦板块海水相通,致使哈萨克斯坦板块广大海域出现南、北动物群混生现象。早石炭世末,三大板块海域相连,除各地沉积和构造古地理环境尚有差异外,中石炭世开始,腕足类,类及珊瑚等动物群均显示出明显的一致性。 相似文献
155.
新疆乌恰县莎里塔什组生物地层新知 总被引:2,自引:0,他引:2
对新疆乌恰县塔塔村下侏罗统莎里塔什组孢粉植物群的研究,共发现孢粉22属26种,植物化石12属15种。根据这些孢粉化石建立了一个孢粉组合,命名为Cyathidites-Classopollis组合,再根据侏罗纪的标志植物锥叶蕨(Coniopteris)的存在,将莎里塔什组的时代确定为早侏罗世,为乌恰地区早侏罗世生物地层提供了可靠依据 相似文献
156.
黔南地区花岗石资源丰富。绿色花岗石矿体由辉长辉绿岩(内部岩相)、辉绿岩(过渡岩相)和辉绿玢岩(边缘岩相)以及钠长石脉岩组成,以过渡岩相辉绿岩体为石材主要开采对象。矿体厚度大,分布广,成荒率高,石材花色品种好,具有很大开发前景 相似文献
157.
Oxygen Isotope Exchange Kinetics Between Coexisting Minerals and Water in the Aral Granite Pluton of the Altay Mountains, Northern Xinjiang 总被引:2,自引:0,他引:2
Liu Wei Research Center of Mineral Resources Exploration Chinese Academy of Sciences Chinese Academy of Sciences BeijingHe Baichu Changsha Institute of Geotectonics Chinese Academy of Sciences Changsh Hunanand Chen ZhenshengYichang Institute of Geology Mineral Resources Chinese Academy of GeologicalSciences Yichang Hubei 《《地质学报》英文版》1996,70(4)
Coexisting quartz, feldspar and biotite vary widely in their δ18O values and display a remarkable 18O/16O disequilibrium relation; especially, a quartz-feldspar reversal (△ 18OQUartz_feldspar< 0) exsists in the Aral granite pluton of the Altay Mountains, northern Xinjiang. The 18O / 16O exchange reaction definitely occurred between granite and water. Initial δ18O values of the granite and exotic fluid are evaluated by the mass balance consideration. The conventional method of discrimination between various magma derivations simply with δ18O values of either whole rock or separate minerals is misleading and unreliable. Experiments carried out by the authors show that the 18O / 16O exchange reaction is not accompanied by what geologists describe as petrological and mineralogical alteration effect. This decoupling relation implies that exchange reaction occurs at a relatively high temperature during subsolidus-postmagmatic cooling of magmas. The exchange mechanism is mainly diffusion-controlled. It is 相似文献
158.
In the Dharwar tectonic province, the Peninsular Gneiss was considered to mark an event separating the deposition of the older
supracrustal Sargur Group and the younger supracrustal Dharwar Supergroup. Compelling evidence for the evolution of the Peninsular
Gneiss, a polyphase migmatite, spanning over almost a billion years from 3500 Ma to 2500 Ma negates a stratigraphic status
for this complex, so that the decisive argument for separating the older and younger supracrustal groups loses its basis.
Correlatable sequence of superposed folding in all the supracrustal rocks, the Peninsular Gneiss and the banded granulites,
indicate that the gneiss ‘basement’ deformed in a ductile manner along with the cover rocks. An angular unconformity between
the Sargur Group and the Dharwar Super-group, suggested from some areas in recent years, has been shown to be untenable on
the basis of detailed studies, A number of small enclaves distributed throughout the gneissic terrane, with an earlier deformational,
metamorphic and migmatitic history, provide the only clue to the oldest component which has now been extensively reworked. 相似文献
159.
Rapid Variscan exhumation and the role of magma in core complex formation: southern Brittany metamorphic belt, France 总被引:6,自引:0,他引:6
ABSTRACT The high-grade migmatitic core to the southern Brittany metamorphic belt has mineralogical and textural features that suggest high-temperature decompression. The chronology of this decompression and subsequent cooling history have been constrained with 40Ar/39 Ar ages determined for multigrain concentrates of hornblende and muscovite prepared from amphibolite and late-orogenic granite sheets within the migmatitic core, and from amphibolite of the structurally overlying unit. Three hornblende concentrates yield plateau isotope correlation ages of c. 303–298 Ma. Two muscovite concentrates record well-defined plateau ages of c. 306–305 Ma. These ages are geologically significant and date the last cooling through temperatures required for intracrystalline retention of radiogenic argon. The concordancy of the hornblende and muscovite ages suggest rapid post-metamorphic cooling. Extant geochronology and the new 40Ar/39Ar data suggest a minimum time-integrated average cooling rate between c. 725 °C and c. 125 °C of c. 14 ± 4°C Ma-1, although below 600 °C the data permit an infinitely fast rate of cooling. Mineral assemblages and reaction textures in diatexite migmatites suggest c. 4 kbar decompression at 800–750 °C. This must have pre-dated the rapid cooling. Emplacement of two-mica granites into the metamorphic belt occurred between 345 and 300 Ma. The youngest plutons were emplaced synkinematically along shallow-dipping normal faults interpreted to be reactivated Eo-Variscan thrusts. A penetrative, west-plunging stretching lineation developed in these granites suggests that extension was orogen-parallel. Extension was probably related to regional uplift and gravitational collapse of thermally weakened crust during constrictional (escape) tectonics in this narrow part of the Variscan orogen. This followed slab breakoff during the terminal stages of convergence between Gondwana and Laurasia; detachment may have been consequent upon a change in kinematics leading to dextral displacement within the orogen. Dextral ductile strike-slip displacement was concentrated in granites emplaced synkinematically along the South Armorican Shear Zone. Rapid cooling is interpreted to have resulted from tectonic unroofing with emplacement of granite along decollement surfaces. The high-grade migmatitic core of the southern Brittany metamorphic belt represents a type of metamorphic core complex formed during orogen-parallel extensional unroofing and regional-scale ductile flow. 相似文献
160.
冀西北侏罗系一个新的地层单位——阳眷组 总被引:1,自引:1,他引:1
记述侏罗系一个新的地层单位——阳眷组,用以代表张家口地区下花园组(巴柔期)之下,古老地层(前寒武纪或奥陶纪)之上的沉积。阳眷组以砂岩、泥岩为主,底部有一层粗砂岩夹砾岩、砂砾岩透镜体,不整合于冶里组或雾迷山组之上,顶部有一层稳定的菱铁质鲕粒泥岩与下花园组为界;中、上部多为紫红色或杂色,与上覆的含煤地层差别明显;时代可能属早侏罗世晚期。 相似文献