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长江源区的火山岩包含了青藏高原北部新生代火山岩形成及演化的全部信息，其年代学研究对查明青藏高原北部新生代火山活动时空演化具有重要意义。通过K—Ar同位素年代学研究，将长江源区新生代的火山活动划分为3期：第Ⅰ期(40．1-35．1Ma)火山喷发较弱，形成小范围分布的细粒安粗岩和斑状粗面岩；第Ⅱ期(26．5～17．6Ma)火山喷溢最为强烈，形成大面积厚层黑色气孔状安粗岩；第Ⅲ期(5．5-4．61Ma)由潜火山作用形成球粒状、斑状粗面岩岩丘。长江源区3个期次的火山喷发与青藏高原北部火山活动的阶段性相对应。长江源区新生代火山岩的演化特征为：从早到晚，岩石系列由高钾钙碱性系列→钾玄岩系列演化；岩性由安粗岩→粗面岩演化。 相似文献
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藏北高原新生代火山岩地球化学系列划分及成因分析 总被引：4，自引：0，他引：4
根据K—Ar法和Ar-Ar法定年数据，藏北新生代火山岩从早到晚可划分为多格错仁和走构油茶错高钾钙碱性系列(40—30Ma)、巴毛穷宗和鱼鳞山白榴石碧玄岩—响岩系列(29—24Ma)以及黑石北湖钾玄岩系列(1．5Ma)。从岩石化学和同位素方面对区内新生代火山岩进行了研究，认为藏北新生代火山岩同时具有板内碱性玄武岩和岛弧玄武岩的双重地球化学特征。在成因和源区上各系列存在着差异，高钾钙碱性系列为富集地幔玄武岩底侵作用导致地壳物质部分熔融的产物，并经历了地壳的AF过程。而白榴石碧玄岩—响岩系列和钾玄岩系列来自与古俯冲有关的“古老富集地幔”，为岩浆分离结晶作用的产物。岩浆起源深度随时间变新逐渐变大。 相似文献
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北京燕山构造旋回安粗岩系 总被引：4，自引：0，他引：4
安粗岩系是指由钾质粗面玄武岩，橄榄玄武粗安冉、安粗岩，粗面岩和高钾流纹岩等富钾岩石组成的火山岩系列。本文以北京地区燕山构造旋回安粗岩系火山岩为例，通过与国内外公认的安粗岩系比较，以及对不同系列火山岩特征的对比分析，明确提出：安粗岩系是可以与拉斑玄武岩系、钙碱性岩系和碱性玄武岩系并列存在的独立的火山岩系列，它有自己特写的产出环境，有别于其他岩系的岩石类型，岩石组合及物质成分等特点。 相似文献
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根据TAS图解，北京市北部凤舵梁－四海地区东岭台组火山岩属于流纹岩－粗面岩－粗安岩组合。该套火山岩既不属于钾玄岩系列，也不是典型的高钾钙碱性系列或碱性橄榄玄武岩系列，在总体上应属于钾质碱性纱列和富钾质拉五系列相混合的过渡岩石组合。该套火山岩轻稀土明显富集。粗安岩类岩石没有负铕异常负铕异常不明显，而流纺岩和粗面岩存在明显的负铕异常。凤舵梁－四海地区东岭台组酸性火山岩形成于造山晚期或后造山期初始阶段。 相似文献
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华北板块南缘熊耳群火山岩岩石类型及火山岩系列 总被引：2，自引：0，他引：2
基于大量的岩相学和岩石化学资料，作者认为，熊耳群火山岩的岩石类型主要为橄榄玄粗岩，安粗岩，粗面英安岩和流纹岩，其次为高钾玄武安山岩、橄榄粗安岩，高钾安山和高钾英安岩；火山岩系列主要为橄榄玄粗岩系，其次为高钾钙碱性岩系；熊耳群火山岩可能是大陆边缘弧弧后火山岩或碰撞后弧火山岩。同时，作者在文中列出了４４个代表性火山岩样品的岩石化学资料和９１３个火山岩，次火山－侵入岩样品的平均化学成分资料。 相似文献
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西天山玉希莫勒盖达坂玄武安山岩—高钾玄武安山岩—粗安岩组合的发现及其地质意义 总被引：6，自引：3，他引：3
在阿吾拉勒东段玉希莫勒盖达坂地区大哈拉军山组主要是一套以安山质（粗安质）-英安质（粗面质-粗面英安质）火山熔岩和火山碎屑岩为主的火山岩建造。根据岩石地球化学特征,本文在大哈拉军山组火山岩的上部厘定出了钙碱性玄武安山岩—高钾钙碱性玄武安山岩—粗安岩（橄榄安粗岩系）组合。微量元素地球化学特征显示,三类岩石形成于岛弧环境,钙碱性玄武安山岩的形成与板片俯冲作用有关,而高钾钙碱性玄武安山岩和粗安岩的形成则与俯冲板片断裂诱发的软流圈上涌作用有关。钙碱性玄武安山岩—高钾钙碱性玄武安山岩—粗安岩组合的存在说明阿吾拉勒东段在晚石炭世由于俯冲板片的断裂,构造体制由挤压转变为伸展。玉希莫勒盖达坂大哈拉军山组上部的火山岩组合与世界许多著名铜-金矿集区（如Papua New Guinea）的火山岩组合相似,显示该地区晚石炭世具有良好的铜、金成矿条件。 相似文献
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藏北新生代火山岩系列的地球化学及成因 总被引：1，自引：0，他引：1
自始新世 (4 5Ma)印度板块和欧亚板块碰撞以来 ,藏北新生代火山活动相当频繁 ,在空间上自南向北随时间早晚依次形成了羌塘、可可西里和喀喇昆仑—玉门 3个火山岩带 ,依岩石组合和地球化学特征可划分为 5个火山岩系列 :①钠质碱性玄武岩系列 ;②白榴石碧玄岩 -响岩系列 ;③高钾钙碱性系列 ;④可可西里钾玄岩系列 ;⑤喀喇昆仑—玉门钾玄岩系列。通过对各系列火山岩成因的研究 ,可以作为了解新生代以来青藏高原岩石圈物质组成、壳幔结构以及高原隆升机制的重要窗口 相似文献
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青藏高原北部新生代走构油茶错、纳丁错火山岩年代学、地球化学特征及其构造意义 总被引：2，自引：2，他引：0
本文对分布于藏北南羌塘地区的走构油茶错和纳丁错新生代火山岩进行了岩石学、同位素年代学和地球化学研究.两个地区火山岩主要由粗面玄武岩、橄榄粗安岩、安粗岩及粗面岩组成,具有从碱性系列火山岩到高钾钙碱性火山岩连续演化的特征.锆石U-Pb定年表明两个地区火山岩形成时代分别为34.64±0.55Ma和35.03±0.54Ma,另外在走构油茶错安粗岩和粗面岩中发现了大量的捕获锆石.地球化学分析显示,岩石ε_(Hf)(t)均为正值,但随SiO_2含量的增高,ε_(Hf)(t)有减小的趋势.稀土元素配分曲线上轻重稀土分馏明显,无或轻微Eu负异常,尤其是重稀土出现分馏,大多数样品(Sm/Yb)_N值介于6.30～8.25之间,表明原生岩浆起源于含有石榴石的弱亏损型软流圈地幔,中酸性岩浆所具有的类似埃达克岩的地球化学特征是原生幔源岩浆经AFC作用形成的.始新世末期南羌塘地区的火山活动可能与向北俯冲的拉萨地块的岩石圈地幔断离造成的软流圈上涌有关. 相似文献
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横路矿区位于朱溪矿集区内,其成矿条件与世界最大钨矿床--朱溪矿床类似,目前已发现了多处找矿线索,但前期工作主要聚焦于500 m以浅,亟待探索该区深部找矿前景。本文从矿区地质、地球物理、地球化学、遥感特征及钻探验证等方面综合分析,并与朱溪矿区进行对比,发现二者在成矿地层层位、控岩控矿构造以及岩浆岩所处成岩-成矿事件等重要成矿条件上极为相似。此外,横路矿区的浅表矿化蚀变分布情况与岩脉密切相关,物化探异常及岩脉分布特征显示深部存在隐伏岩体。综合分析认为横路矿区深部找矿潜力巨大,具有找寻破碎带(热液脉)型、矽卡岩型及斑岩型铜钼金多金属矿床的良好前景。 相似文献
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石平川钼矿位于浙江省青田县黄垟乡石平川村―底黄垟村一带,经过几十年的开发资源储量已经不多。通过对石平川地区地质、地球物理、地球化学等方面研究表明:矿床受石平川火山穹窿控制,在其外围还有多个火山机构存在迹象;地球重力异常表明石平川外围地区存在与石平川岩体相似的隆起区,有相应的地球化学组合异常区。这三者之间构成了有机整体,表明本区具有良好的成矿远景。 相似文献
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In March and April 1972, 380 gravity stations were established in the T.F.A.I. The data were reduced to Bouguer anomalies of 5 mGal isolines. Qualitative and quantitative interpretation based on the gravity map, on seismic data and on the magnetics and physiography of the area revealed that: The crust of the Gulf of Tadjura and the central part of the T.F.A.I. is strongly oceanized and is the direct continuation of the Sheba Ridge.To the north of the Gulf, at the Dankali Mountains, the crust increases in thickness and most probably contains sialic fragments, indicating the continuation of the Danakil Chains in the T.F.A.I.To the south, the structure is bordered by a continental block, the Aysha Horst. The oceanization is concentrated only in the area of deep injections, marked by gravity maxima, whereas the rest of the area is to be described as sub-continental. The crust is attenuated from south (Aysha Horst) to north (Red Sea), from 30 to 15 km in thickness.The pattern of the gravity anomalies shows clearly liniations only along the coasts of the Gulf of Tadjura and the Straits of Bab el Mandeb. Inland the field breaks up into relative minima and maxima, indicating the fragmentation of the crust and the ‘triple junction’ nature of the area.The tectonic process is that of extension, with normal faults having maximum displacements at the northern border of the Gulf of Tadjura.The uppermost mantle has low velocity and density values due to thermal processes in the expanding zone. The state of the upper-mantle material must be that of partial melting due to high temperatures of the order of 800° to 1,000° C at about 15 km depth. 相似文献
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Numerous ge ological and geophysical investigations within the past decades have shown that the Rhinegraben is the most pronounced segment of an extended continental rift system in Europe. The structure of the upper and lower crust is significantly different from the structure of the adjacent “normal” continental crust.
Two crustal cross-sections across the central and southern part of the Rhinegraben have been constructed based on a new evaluation of seismic refraction and reflection measurements. The most striking features of the structure derived are the existence of a well-developed velocity reversal in the upper crust and of a characteristic cushion-like layer with a compressional velocity of 7.6–7.7 km/sec in the lower crust above a normal mantle with 8.2 km/sec. Immediately below the sialic low-velocity zone in the middle part of the crust, an intermediate layer with lamellar structure and of presumably basic composition could be mapped.
It is interesting to note that the asymmetry of the sedimentary fill in the central Rhinegraben seems to extend down deeper into the upper crust as indicated by the focal depths of earthquakes. The top of the rift “cushion” shows a marked relief which has no obvious relation to the crustal structure above it or the visible rift at the surface. 相似文献
16.
A.R. Ritsema 《Tectonophysics》1979,53(3-4)
A general review of relevant data on the conditions for and the occurrence and distribution of catastrophic earthquakes in Europe is presented. A table of some important events is included. 相似文献
17.
Reliable fault plane solutions of shallow earthquakes and information on surface fault traces in combination with other seismic, geomorphological and geological information have been used to determine the orientation and other properties of the seismic faults in the Aegean and surrounding area.Thrust faults having an about NW-SE strike occur in the outer seismic zone along western Albania-westernmost part of mainland of Greece-Ionian Sea-south of Crete-south of Rhodes.The inner part of the area is dominated by strike-slip and normal faulting. Strike-slip with an about NE-SW slip direction occurs in the inner part of the Hellenic arc along the line Peloponnesus-Cyclades-Dodecanese-southwest Turkey as well as along a zone which is associated with the northern Aegean trough and the northwesternmost part of Anatolia. All other regions in the inner part of the area are characterized by normal faulting. The slip direction of the normal faults has an about SW-NE direction in Crete (N38°E) and an about E-W direction (N81°E) in a zone which trends N-S in eastern Albania and its extension to western mainland of Greece. In all other regions (central Greece-southern Yugoslavia and Bulgaria, western Turkey) the slip of the normal faults has an about N-S direction. 相似文献
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R. B. Ogendo Dr. 《GeoJournal》1978,2(5):451-462
The paper opens with a brief examination of the Nairobi City pattern of industrial location (especially in terms of industrial areas), including the enumeration of some of the industries involve (a number of them located outside the city boundary). Industrial structure (cum-location) aspects, both in the city and in the neighbouring districts of Kiambu, Machakos and Kajiado (which together constitute the Nairobi Area), are next discussed in detail. The data used are those from the 1965 and 1975 research surveys, and are presented on a national basis so as to demonstrate the significance or otherwise of the Nairobi Area as the industrial core of Kenya. The discussion of the location factors in the Nairobi Area brings the paper to a close. Incorporated are seven tables and four maps. 相似文献
19.
B.C Papazachos 《Tectonophysics》1976,33(1-2)
Data concerning the focal mechanism and the spatial distribution of earthquakes have been used to investigate the active tectonics of the northern Aegean and the surrounding area.A thrust region, which includes the northernmost part of the Aegean and at least part of the Marmara Sea, has been defined. An amphitheatrical Benioff zone dipping towards the thrust region from south, east and probably from west, at a mean angle of about 30°, has been detected.The thrust region is surrounded by a region of normal faulting. An eastward progression of the seismic activity in this normal faulting region between 1954 and 1971 has been observed.A correspondence between the earthquake occurrence in the thrust and normal faulting regions has also been observed. Each large shock produced by tensional mechanism in the region of normal faulting is preceded or followed by one or more shocks of compressional mechanism in the thrust region.The focal mechanism, the distribution of the earthquake foci with intermediate focal depth, as well as some magnetic and gravimetric observations can be interpreted by assuming that dense oceanic crust sinks in the northern part of this area and that the adjacent lithosphere moves by segmentation to fill the void with the consequence of producing tensile stresses associated with normal faulting. Such a mechanism of lithospheric interaction suggests that accretion probably takes place in this area. 相似文献
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近年来，对柴达木北缘达肯达坂群的研究取得一系列重要进展。如在绿梁山—锡铁山—都兰带原定的达肯达坂群中厘定出一条长350km的加里东期榴辉岩带，其地质意义已进行过广泛的讨论［1～3］。最近，在这个带的北部乌兰地区进行的1∶5万地质填图中，又有基性麻粒岩出露的报道；我们在1999年的野外工作中，在青海省德令哈市附近原定为古元古代（？）达肯达坂群的长英质片麻岩中发现有基性麻粒岩存在，从区域走向及岩石的基本特征来看，它们与乌兰地区发现的基性麻粒岩相似，可构成一条NWW—SEE走向的麻粒岩带，这一麻粒岩带的厘定及形成时代… 相似文献