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1.
内蒙古东乌旗碱性侵入岩的时代、成因及地质意义 总被引：3，自引：0，他引：3
内蒙古东乌旗西部的碱性侵入岩为碱性花岗岩和石英正长岩组合,含钠铁闪石.采用LA-MC-ICP-MS锆石U-Pb法对2件碱性花岗岩样品进行年代学研究.定年结果分别为272.3±0.7 Ma和271.7±0.7 Ma,属早二叠世晚期.13件样品的地球化学数据显示:碱性花岗岩具高SiO2(72.62％～78.46％),富碱(K2O+Na2O=7.54％～9.80％),贫CaO(0.66％～0.91％)、MgO(0.07％～0.31％)的特征,铝饱和指数A/CNK为0.87～0.99,碱性指数NK/A为0.91～1.04,属准铝质-过碱质碱性岩系列;稀土总量中等(∑REE=146.4×10-6～389.0×10-6),轻重稀土分馏均较弱-(La/Yb)N 3.74～6.83],强烈的负Eu异常(δEu为0.12～0.36);贫Ba、Sr、P、Ti,富Rb、Th、U、Hf等元素,显示“A1”型花岗岩的特征.石英正长岩与碱性花岗岩相比较,Ba的含量(554×10-6～1230×10-6)显著高于后者(Ba=74×10-6～207×10-6),Eu负异常缺失(δEu=0.94～1.24),可能由岩浆源区深度的差异造成的.二者均具非常低Sr(27.20×10-6～157.00×10-6,2个样品大于100×10-6)和高Yb(2.08×10-6～7.26×10-6,除P24-11-1为1.36×10-6)的特征,与板内花岗岩特征一致.综上,我们认为东乌旗碱性侵入岩可能为造山后-非造山伸展体制岩浆作用的产物,标志着大约在272Ma兴蒙造山带部分造山演化可能处于造山后向非造山构造转换阶段. 相似文献
2.
兴蒙造山带的构造演化及古亚洲洋的闭合时限尚存在较大争议,沿缝合带出露的花岗岩的侵位时代和成因对于约束古亚洲洋的演化具有重要意义。乌珠新乌苏花岗岩位于兴蒙造山带西段的索伦缝合带内,其Na_2O+K_2O含量为7.14%～9.36%,Al_2O_3含量为13.18%～13.49%,K_2O/Na_2O为1.10～1.52,属于高钾钙碱性系列岩石。稀土总量富集(174.8×10~(-6)～213.7×10~(-6)),相对富集轻稀土元素,轻重稀土分异中等[(La/Yb)_N=3.68～5.41],Eu负异常明显。乌珠新乌苏花岗岩富集Rb、Th、Hf,亏损Nb、Sr、P、Ti等元素,符合典型高分异A型花岗岩的低Sr、高Yb、Eu负异常的特点,显示后碰撞花岗岩的特征,形成于造山后地壳减薄阶段。乌珠新乌苏花岗岩锆石LA-ICP-MS U-Pb定年显示其~(206)Pb/~(238)U加权平均年龄为279±2.7Ma(MSWD=1.6)和276±1.9Ma(MSWD=0.69)。正的全岩ε_(Nd)(t)值(2.1～2.7)和锆石ε_(Hf)(t)值(7.7～10.2)以及相对年轻的亏损地幔模式年龄(Nd的t_(DM2)为826～874Ma;Hf的t_(DM2)为655～931Ma),表明乌珠新乌苏花岗岩母岩浆可能来源于新元古代新生下地壳的部分熔融。综合花岗岩的地质地球化学、年代学及同位素特征,认为兴蒙造山带西段的乌珠新乌苏地区在早二叠世处于后碰撞的伸展环境。 相似文献
3.
新疆东准噶尔黄羊山碱性花岗岩体的锆石U-Pb年龄和岩石成因 总被引：17，自引：0，他引：17
新疆东准噶尔卡拉麦里构造带分布有多种类型花岗岩,主要包括花岗闪长岩、二长花岗岩、碱长花岗岩和碱性花岗岩.对其中最大的碱性花岗岩体(黄羊山岩体)进行定年和地球化学组成研究,结果显示,岩体的年龄约为305 Ma,岩石富含钠质角闪石(钠闪石、钠铁闪石)和少量霓石,具低铝、富碱、贫钙镁及低铁的主量元素特征,其微量元素明显富集Rb、Th等大离子亲石元素和Zr、Hf等高场强元素而强烈亏损元素Ba、Sr、Eu,稀土元素配分模式呈典型的平坦‘V'字型.这些矿物学和地球化学组成特征表明黄羊山碱性花岗岩属于典型的A型花岗岩.认为幔源岩浆高度分异、麻粒岩相残留岩及I型英云闪长质-花岗闪长质岩石部分熔融等A型花岗岩成岩模式不能解释黄羊山碱性花岗岩的成因.根据岩石的εNd(t)= 5.9～ 6.5,比当时洋壳的εNd(t)值低3～4个ε单位,认为形成该岩体的岩浆可能来源于花岗闪长质岩浆的分异结晶,而花岗闪长质岩浆则主要是玄武质洋壳和少量大洋沉积物(约5%)部分熔融的产物. 相似文献
4.
青山堡岩体位于阿拉善弧型构造南缘之龙首山隆起中段,紧邻芨岭岩体,是龙首山-祁连山铀矿成矿带的重要组成部分。为了理清岩体源区性质和演化过程,还原大地构造动力学背景,对青山堡岩体进行系统的地质地球化学研究。常量元素地球化学分析显示,青山堡岩体属于富硅富钾的钙碱性花岗岩类;稀土元素方面,细晶花岗岩呈现出平缓的配分曲线、强烈的Eu谷特征(δEu=0.05),而其余花岗岩类样品均呈现出明显的配分曲线右倾趋势,Eu谷程度较小(δEu=0.43～0.89);微量元素方面,各岩体样品基本均富集Th,U,Nb,Zr,Hf等高场强元素和La,Nd,Y,Lu等稀土元素,亏损大离子亲石元素Ba,Sr,P和高场强元素Ti等,而细晶花岗岩具有极低的Sr值(9.4)和非常高的Yb值(9.34);青山堡岩体中粗粒钾长花岗岩的锆石U-Pb年龄为441.6±4.2 Ma(MSWD=1.4,n=14),细晶花岗岩的锆石U-Pb年龄为430.1±5.6 Ma(MSWD=1.8,n=11),与阿拉善地块的碰撞运动时间(加里东晚期)相一致;全岩Sr-Nd同位素分析显示青山堡岩体具有较低的初始(~(87)Sr/~(86)Sr)_i比值(0.663 767～0.707 767)和较低的εNd(t)负值(-0.1～-7.4),其应起源于古元古代龙首山群古老基底地壳物质的重熔,但也有部分地幔物质的贡献。综合分析认为,青山堡岩体除细晶花岗岩外均形成于阿拉善地块与北祁连岛弧的碰撞造山运动,为I型花岗岩;而细晶花岗岩应是碰撞造山作用期后伸展运动的产物,属于A型花岗岩。 相似文献
5.
新疆巴里坤县大加山一带碱性花岗岩的特征及构造环境探讨 总被引：2，自引：0，他引：2
大加山一带的碱性花岗岩按侵入先后可分为碱长花岗岩单元、钠闪石碱性花岗岩单元、霓石钠门石碱性花岗岩单元，由它们构成大加山超单元。这些岩石大都含碱性暗色矿物，从矿物组合看具贫水特征，岩石化学方面显示高硅、高碱、贫铝、镁、钙等特征；微量元素显示钾、铷、钍富集，锶、钡等强烈亏损特点；稀土元素总量较高，轻稀土较重稀土富集，并具有强的负铕异常。就位机制为断裂扩张并具顶蚀型被动定位类型，同源岩浆演化具反序列演化特点。上述特征和区域构造环境分析表明，大加山一带碱性花岗岩为非造山环境下形成的Ａ型花岗岩。 相似文献
6.
风雷山二长花岗岩位于北山北部的红石山—百合山—蓬勃山与芨芨台子—小黄山两条蛇绿混杂岩带之间,构造位置特殊。二长花岗岩LA-ICP-MS锆石U-Pb年龄加权平均值为(320±1)Ma,代表了其成岩年龄。岩石具有富SiO2、Al2O3的特征,里特曼指数(σ)为1.58～2.74(3.3),碱度率(AR)为2.35～4.05,属于钙碱性花岗岩类,A/NCK=0.92～1.15,显示出偏铝质、过铝质岩浆的特征。稀土元素总量(ΣREE)较高,稀土配分模式呈轻稀土富集的右倾型[(La/Yb)N=4.60～8.83],轻稀土分异程度大于重稀土,所有样品均具有Eu负异常(δEu=0.56～0.88,平均为0.72);强烈富集强不相容元素Th、U和大离子亲石元素Rb、K,亏损高场强元素Nb、Ta、Ti、P。曲线形态与上地壳的相似,表明岩浆作用过程有上地壳物质的参与。高的Th含量(8.58～21.62μg/g)及低的Nb/Ta值(8.75～15.72)指示岩浆源区主要为地壳。在Rb-(Nb+Y)及R1-R2等构造判别图解中样品大多数落入板块碰撞前火山弧花岗岩区,根据岩石共生组合特征,认为风雷山地区二长花岗岩为碰撞前陆缘弧岩浆作用的产物,与红石山—百合山—蓬勃山有限洋的洋壳俯冲作用有关。结合区域地质背景,推测红石山—百合山—蓬勃山有限大洋的闭合时间应晚于晚石炭世早期。 相似文献
7.
京格斯台碱性花岗岩出露于内蒙古东乌旗西北部的中蒙边境一带,是准噶尔-南蒙古-内蒙古碱性花岗岩带的一部分,为一套含钠铁闪石碱性花岗岩类。锆石LA-MC-ICPMS U-Pb测年获得了301.3±1.5Ma(n=21,MSWD=1.3)的年龄,表明侵位时代为晚石炭世。全岩地球化学分析显示样品具有高SiO2(75.16%~76.96%)、高碱(K2O=4.61%~5.04%,Na2O=3.98%~4.24%)、贫CaO(0.08%~0.25%)、MgO(0.07%~0.1%),低FeOt(1.05%~2.05%),高的FeOt/MgO比值(12.85~29.66),属于弱过铝质系列;富集Rb、Th、U、K等大离子亲石元素及Zr、Hf等高场强元素,弱亏损Nb、Ta,强烈亏损Ba、Sr、P、Ti等;稀土元素总量较低[ΣREE范围为(70.19~193.93)×10~(-6),平均值为126.82×10~(-6)],轻稀土略富集,具有明显的Eu负异常(δEu=0.03~0.07),呈类似"海鸥"型稀土配分模式。岩石学及地球化学特征表明京格斯台碱性花岗岩属于碱质A型花岗岩。锆石原位Hf同位素和全岩Nd同位素分析显示其具有亏损的Hf-Nd同位素组成εHf(t)和εNd(t)均为正值,Hf地壳存留模式年龄范围为385~1605Ma,并且多数集中于600~900Ma,二阶段Nd模式年龄范围为582~650Ma,这表明源岩为幔源新生地壳物质,代表了新元古代一次地壳增生。综合岩石学、岩石地球化学和同位素地球化学数据,我们认为京格斯台碱性花岗岩是由新生地壳,在晚石炭世贺根山洋闭合后的后造山伸展阶段,在上涌软流圈的加热及减压作用下部分熔融形成的,形成于后造山构造环境。 相似文献
8.
东乌珠穆沁旗京格斯台碱性花岗岩出露于中蒙边界附近的京格斯台地区,1.20万区域地质调查归之于华力西晚期(K γ3(2)4)和印支期(γ15)侵入体,是兴蒙造山带南带碱性花岗岩的一部分.该岩石具高硅、富碱、准铝、贫镁钙的特点,SiO2含量为74.8%～78.7%,K2O＞Na2O,全碱含量大于8.0%,属于过碱性和碱性花岗岩类(PAG).岩石稀土总量偏低,轻重稀土元素分馏程度不明显,(La/Yb)N值0.898.84～5.168,6Eu为0.07～0.89,铕强烈亏损.为后造山伸展环境下的产物.采用单颗粒锆石U-Pb同位素稀释法测定京格斯台碱性花岗岩的年龄,206Pb/238U表面年龄加权平均值为(284.8±1.1)Ma.为早二叠世岩浆活动的产物. 相似文献
9.
北京白查A型花岗岩的地球化学特征及其成因与构造指示意义 总被引：17，自引：6，他引：11
位于北京昌平区的年龄为127Ma的白查岩体是一个晶洞过碱性花岗岩岩株，其侵位于燕山造山带西段的八达岭岩基中。白查岩体具有高硅、Zr、Ga、Pb、HFSE和REE含量，高Fe/Mg和Ga/Al比值，强烈亏损Ca、Sr、Eu，具有亏损放射性成因Pb同位素的特征。白查岩体属于Dall’Agnol和Oliveira (2007)定义的典型的还原型A型花岗岩，其地球化学特征与燕山带中生代晚期的后石湖山(山海关)和窟窿山A型花岗岩非常相似。白查花岗岩起源于华北克拉通下地壳镁铁质源岩在相对贫水、高温、低氧逸度条件下的低程度部分熔融。综合区域地质背景和该岩体的成岩机制判断，白查花岗岩的形成标志燕山西段造山崩塌阶段的到来。除浙江东南瑶坑过碱性花岗岩外，白查岩体是具有A1型花岗岩元素地球化学特征但并非形成于非造山大地构造背景的过碱性花岗岩的又一个实例。 相似文献
10.
义敦岛弧是三江特提斯复合造山带的重要组成部分。文章对义敦岛弧海子山花岗岩体进行锆石U-Pb年代学、全岩地球化学及Sr-Nd-Pb同位素地球化学进行分析,探讨其成因与构造意义。海子山花岗岩锆石U-Pb年龄为93.7±1.1 Ma(MSWD=2.1, 2σ),为晚白垩世早期岩浆活动产物,岩石具高硅、富碱的特征,铝饱和指数A/CNK=1.04～1.12,属于弱过铝质岩石。稀土配分曲线呈燕式分布,Eu/Eu~*=0.05～0.32,具有明显的Eu负异常。富集Rb、Th、U、Ta、Pb等元素,明显亏损Ba和Sr,表现出A型花岗岩的特征。岩石的ε_(Nd)(t)=–4.8～-3.4,二阶段模式年龄T_(DM2)=0.91～1.00 Ga,结合岩石的Pb同位素特征及低的CaO/Na_2O比值与高的Al_2O_3/TiO_2比值,说明其应起源于泥质岩石的部分熔融并有少量地幔组分加入。综合地球化学、同位素特征及义敦岛弧地区构造资料,表明海子山花岗岩是造山后伸展背景下形成的A型花岗岩,为地壳拉张、减薄,软流圈地幔上涌引起中上地壳泥质岩部分熔融的产物,具有壳幔物质混合的特征。 相似文献
11.
摩擦桩基桩土间极限摩阻力取值问题探讨 总被引：1，自引：0，他引：1
通过对广珠东线高速公路横沥大桥的试桩及土体的工程地质条件分析,总结出影响摩擦桩基桩土间极限摩阻力取值的一般问题以及解决问题的方法和措施。 相似文献
12.
位于华北和扬子两板块碰撞带中的苏鲁榴辉岩形成的温压条件不但是超高压，而且是高温。榴辉岩的PTt轨迹表明其为陆-陆磁撞俯冲带的产物。榴辉岩的区域性围岩花岗质片麻岩为新元古代同碰撞期花岗岩，榴辉岩及其他直接围岩皆呈包体存在于其中，并见新元古代花岗岩呈脉状侵入榴辉岩包体中。区域性围岩新元古代花岗岩的锆石中发现有柯石英、绿辉石等包裹体，表明新元古代花岗岩的组成物质也经受过超高压变质作用，且榴辉岩与围岩新元古代花岗岩的锆石U-Pb体系同位素年龄基本相同。但新元古代花岗岩所记录的变质作用和变形作用期次（或阶段）却少于榴辉岩。椐上述可得如下推断：超高压榴辉岩与新元古代花岗岩岩浆是同时在碰撞带底部（俯冲板块前部）形成的；榴辉岩的第一折返阶段是由新元古代花岗岩岩浆携带上升的，其第二折返阶段是和新元古代花岗岩一起由逆冲及区域性隆起而上升，遭受剥蚀。 相似文献
13.
某高速公路下伏煤矿采空区稳定性分析 总被引：10，自引：0，他引：10
在论述某高速公路下伏砦脖煤矿采空区地质、采矿和工程地质特征的基础上，进行了稳定性数值模拟分析，定性与定量地分析与评价了该煤矿采空区的地表变形特征及稳定性。研究结果表明：该煤矿采空区的变形尚未完成，对拟建的高速公路将产生很大的危害，必须采取相应的工程治理措施。 相似文献
14.
The Importance of the Precipitation and the Susceptibility of the Slopes for the Triggering of Landslides Along the Roads 总被引：3，自引：1，他引：2
Clemente Irigaray Francisco Lamas Rachid El Hamdouni Tomás Fernández José Chacón 《Natural Hazards》2000,21(1):65-81
In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning. 相似文献
15.
混凝剂处理钻井废泥浆液的研究 总被引：4，自引：0，他引：4
通过烧杯搅拌实验对混凝剂处理钻井废泥浆液进行研究，从混凝剂适应PH值范围、混凝效果、沉降速度三方面研究比较，找出一种较为理想的混凝剂，并分析了影响混凝剂性能的主要因素，确定了混凝剂的最佳投放剂量。 相似文献
16.
Guboglo M. N. 《GeoJournal》1980,4(1):53-58
International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen. 相似文献
17.
黄河源区水环境变化及黄河出现冬季断流的原因 总被引：12，自引：0，他引：12
自1954年有水文观测资料以来，黄河曾在青海省玛多县黄河沿水文站发生过3次断流。本文在分析黄河源区水环境特征及其影响因素的基础上指出，鄂陵湖、扎陵湖的环湖融区调节能力低，当遇到连续干旱、冬季其调节水量不足以维系黄河径流时便会发生断流，这是断流的主因。湖水位降低、开采沙金、过度放牧等自然和人为因素也会对黄河发生断流产生影响。鄂陵湖口附近黄河上修建的水电站开始蓄水，提高了两湖及环湖融区的调节能力，今后黄河冬季出现断流的可能性将大为降低。 相似文献
18.
正Artemia cysts are an extremely important component of aquaculture diets.It is well established that the cultivation of fish and shellfish derive substantial health and growth advantages when Artemia are included in the diets of the 相似文献
19.
Climate: Is the past the key to the future? 总被引：2，自引：0，他引：2
The climate of the Holocene is not well suited to be the baseline for the climate of the planet. It is an interglacial, a
state typical of only 10% of the past few million years. It is a time of relative sea-level stability after a rapid 130-m
rise from the lowstand during the last glacial maximum. Physical geologic processes are operating at unusual rates and much
of the geochemical system is not in a steady state. During most of the Phanerozoic there have been no continental ice sheets
on the earth, and the planet’s meridional temperature gradient has been much less than it is presently. Major factors influencing
climate are insolation, greenhouse gases, paleogeography, and vegetation; the first two are discussed in this paper. Changes
in the earth’s orbital parameters affect the amount of radiation received from the sun at different latitudes over the course
of the year. During the last climate cycle, the waxing and waning of the northern hemisphere continental ice sheets closely
followed the changes in summer insolation at the latitude of the northern hemisphere polar circle. The overall intensity of
insolation in the northern hemisphere is governed by the precession of the earth’s axis of rotation, and the precession and
ellipticity of the earth’s orbit. At the polar circle a meridional minimum of summer insolation becomes alternately more and
less pronounced as the obliquity of the earth’s axis of rotation changes. Feedback processes amplify the insolation signal.
Greenhouse gases (H2O, CO2, CH4, CFCs) modulate the insolation-driven climate. The atmospheric content of CO2 during the last glacial maximum was approximately 30% less than during the present interglacial. A variety of possible causes
for this change have been postulated. The present burning of fossil fuels, deforestation, and cement manufacture since the
beginning of the industrial revolution have added CO2 to the atmosphere when its content due to glacial-interglacial variation was already at a maximum. Anthropogenic activity
has increased the CO2 content of the atmosphere to 130% of its previous Holocene level, probably higher than at any time during the past few million
years. During the Late Cretaceous the atmospheric CO2 content was probably about four times that of the present, the level to which it may rise at the end of the next century.
The results of a Campanian (80 Ma) climate simulation suggest that the positive feedback between CO2 and another important greenhouse gas, H2O, raised the earth’s temperature to a level where latent heat transport became much more significant than it is presently,
and operated efficiently at all latitudes. Atmospheric high- and low-pressure systems were as much the result of variations
in the vapor content of the air as of temperature differences. In our present state of knowledge, future climate change is
unpredictable because by adding CO2 to the atmosphere we are forcing the climate toward a “greenhouse” mode when it is accustomed to moving between the glacial–interglacial
“icehouse” states that reflect the waxing and waning of ice sheets. At the same time we are replacing freely transpiring C3
plants with water-conserving C4 plants, producing a global vegetation complex that has no past analog. The past climates of
the earth cannot be used as a direct guide to what may occur in the future. To understand what may happen in the future we
must learn about the first principles of physics and chemistry related to the earth’s system. The fundamental mechanisms of
the climate system are best explored in simulations of the earth’s ancient extreme climates.
Received: 7 November 1996/Accepted: 23 January 1997 相似文献