华北克拉通泊松比与地壳厚度的关系及其大地构造意义   总被引：25，自引：1，他引：24  

嵇少丞  王茜  杨文采 《地质学报》2009,83(3):324-330

华北克拉通破坏和岩石圈减薄已成为我国乃至国际地学界研究的热点之一。本文作者对许卫卫和郑天愉（2005）采用接收函数方法测量渤海湾西北盆岭地区58个宽频地震台站下面地壳厚度和地壳泊松比的资料进行了详细的分析研究。在冀东北、辽西以及石家庄附近的南太行山地区地壳泊松比随地壳厚度增加呈非线性骤然陡降,说明在这些地区中新生代地壳减薄作用主要集中于长英质的中上地壳。在保定—大同和官厅水库—张家口—张北地区,地壳泊松比随地壳厚度增加作缓慢地线性减小,说明由玄武岩浆底侵作用造成的地壳泊松比增加抵消了一部分由长英质中上地壳减薄造成的泊松比减小。所以,在中新生代华北克拉通地壳减薄过程中,上地幔部分熔融及玄武岩浆底侵作用主要集中在保定—大同和官厅水库—张家口—张北等冀西北地区。  相似文献   

Petrology of mafic-ultramafic rocks along North Puruliya Shear zone,West Bengal     

Aditi Mandal  Arijit Ray 《Journal of the Geological Society of India》2009,74(1):108-118

The North Puruliya Shear zone (NPSZ) is characterized by occurrence of mafic-ultramafic rocks aligned parallel to the shear zone, intruding the high grade Proterozoic rocks of Chhotanagpur Gneissic Complex. The ultramafic rocks occur as small lenses, pockets, veins, thin dykes and are intimately associated with mafic (gabbro, norite) rocks. Pyroxenites (viz. olivine websterite, websterite, plagioclase websterite) and hornblendite are the two important members of the ultramafic rocks containing clinopyroxene, orthopyroxene, olivine, plagioclase, amphibole, phlogopite and ilmenite. The mafic-ultramafic rocks show evidence of shearing and retrogressive metamorphism. Linear correlation of chemical attributes suggests fractionation-controlled magmatic differentiation. Enrichment of LILE and LREE in the mafic-ultramafic suite suggests an enriched mantle source and pronounced negative Eu-anomalies in all the rock types except hornblendite suggest fractionation of plagioclase under low f_O2 condition. Progressive iron enrichment trend in rocks of the mafic-ultramafic suite also indicate magmatic differentiation under low f_O2 condition. Early fractionation and accumulation of clinopyroxene and plagioclase from a basaltic magma may have given rise to the ultramafic rocks of the area. Little change in the Nb/Zr and Ce/Zr ratios of ultramafic and mafic rocks (except alkali norite) strongly support low crustal contamination. A few samples of norite and gabbro-norites appeared to be variably contaminated by a crustal component or affected by late granitic intrusion resulting in enrichment of alkali in the former.  相似文献   

小兴安岭东南晚奥陶世鹤林侵入杂岩体成因探讨   总被引：1，自引：0，他引：1  

韩振哲  赵寒冬  吕军  李娟娟  李文龙  王盘喜 《现代地质》2009,23(3)

小兴安岭东南晚奥陶世鹤林侵入杂岩体岩性变化较大,由角闪辉长岩—(石英)闪长岩—英云闪长岩—二长花岗岩组成,不同岩石类型在野外宏观上呈相互侵入、包裹和渐变的接触关系;在(石英)闪长岩、英云闪长岩和二长花岗岩中均发育微细粒闪长质包体,包体多具明显塑性流变特点的浑圆外形和典型岩浆结构、针状磷灰石及捕获的寄主岩钾长石、石英斑晶,为MME型岩浆混合成因包体;杂岩体相对富集LILE(Ba、Sr、Rb)、HFS(U、Th、Zr、Ce)元素等,显示出壳源特点,而较高的εNd(t)值(-2.38~-3.77)显示以幔源为主的特点。研究表明杂岩体具明显的壳幔岩浆混合成因的岩相学、岩石化学和地球化学特征,形成于基性岩浆底侵作用下的陆缘弧型活动大陆边缘构造环境。  相似文献   

粤北白垩纪基性岩脉的年代学和地球化学   总被引：174，自引：23，他引：174  

李献华  胡瑞忠 《地球化学》1997,26(2):14-31

对粤北白垩纪基性岩脉进行了系统的年代学、元素和Ｓｒ－Ｎｄ同位素地球化学研究。基性岩脉主要形成于－１４０Ｍａ、ｄ－１０５Ｍａ、－９０Ｍａ三个阶段，其化学成分以拉斑质玄武岩为主，高的εＮｄ（Ｔ）值（＋５）表明其母岩来源于一大离子亲石元素和轻稀土元素长期较亏损的地幔源。  相似文献   

Geochronology and geochemistry of the Heihe mafic pillow lavas in the Qinling Mountains, China     

张宗清  张国伟  唐索寒  王进辉 《中国科学D辑(英文版)》2001,44(6):517-524

The Qinling Mountains in central China are the joint orogenic zone between the Sino-Korean (or North China) and the Yangtze craton blocks. The age and genesis of the Danfeng mafic volcanics in the north of the Shangzhou-Danfeng fault zone, i.e. the main suture zone in the Qinling orogenic belt, have been controverted for a long time because their age is closely related to the converged time of two blocks. The ages and the geochemical data of the Heihe pillow lavas for the Danfeng mafic volcanics in the Heihe River area in the Qinling orogen are reported in this paper. The obtained isochron age by the Sm-Nd isotopic data of the 13 whole-rock samples for the mafic pillow lavas is 963±130 (2σ) Ma, corresponding to I_Nd = 0.51173±16 (2σ),ɛ _Nd(T)= +6.6, MSWD0.57. However, the Rb-Sr isotopic analytical results for the same samples as the Sm-Nd whole-rock ones are disperse. For the Sm-Nd isotopic systems were interfered during the later geological functions, the Sm-Nd isochron age for the whole-rock sample (Q9511WR) and the mineral phenocrystal samples: amphiboles (Hb) and plagioclases (Plag) presents the better uncertainty, whereas isochron ages of 930 Ma and 437 Ma are given if the WR-Plag and WR-Hb are calculated respectively, and their Rb-Sr isochron age is 268±47(2σ) Ma, I_sr = 0.70475±11 (2σ), MSWD0.96. The major and trace elements for the lavas show that they were formed in the quasi-N-MORB setting.  相似文献   

Gravity anomalies and deep structure of the Andaman arc     

Manoj Mukhopadhyay 《Marine Geophysical Researches》1988,9(3):197-210

The Andaman arc is associated with a major Free-air anomaly pair of mean amplitude 180 mgal. Two-dimensional gravity interpretation suggests significant mass anomalies below the arc that presumably have resulted due to subduction of the Indian plate below the Burma plate. It is inferred that the Andaman trench is of asymmetric V-shape containing about 7 km sediments. An outer bathymetric rise seaward of the trench possibly corresponds to a lithospheric flexure by 500 m. The Cretaceous-Tertiary sediments constituting the Andaman sedimentary arc attain their maximum thickness of about 13 km under the Nicobar. Deep at the subduction zone. At this location a mafic mass is emplaced within the sedimentary section. The underlying oceanic crust apparently experiences phase transition at about 27 km depth in a Benioff zone environment. The Andaman volcanic arc underlies a low density zone that is at least 60 km wide. Along the east margin of the Andaman Sea, cuustal transition presumably occurs below the Mergui Terrace at the Malayan coast.  相似文献   

柴北缘绿梁山高压基性麻粒岩的变质演化历史：岩石学及锆石SHRIMP年代学证据   总被引：9，自引：0，他引：9  

张建新  孟繁聪  于胜尧  戚学祥 《地学前缘》2007,14(1):85-97

高压基性麻粒岩出露在柴北缘HP/UHP变质带的绿梁山地区,它主要呈透镜体状分布在石榴蓝晶(夕线)黑云片麻岩中。岩石学和矿物学数据显示高压基性麻粒岩经历了多阶段变质历史,早期可能经历了榴辉岩相变质作用(p>15kbar),以石榴子石中保留的少量绿辉石为特征;高压麻粒岩组合(Grt-Cpx-Pl-Qtz±Amp±Rt-Ilm)为退变质作用产物,其形成的变质条件为p=9.6~13.5kbar,T=730~870℃。晚期的变质反应以围绕石榴子石和后成合晶生成斜方辉石的为特征,形成的p-T条件为6.2~8.5kbar和720~860℃。高压基性麻粒岩中的锆石SHRIMP测定共获得两组年龄,分别为(448±3)Ma和(421±5)Ma。结合锆石阴极发光和矿物包体研究,前者代表高压麻粒岩阶段的变质年龄,后者代表晚期与斜方辉石形成有关的中低压麻粒岩阶段的变质年龄。这些年龄结果显示麻粒岩相变质作用持续了大约27Ma,这可能与早古生代祁连地块与柴达木地块碰撞作用所引起的地壳加厚和后来的热松驰有关。  相似文献   

太行山北段中生代岩基及其包体锆石U-Pb年代学和Hf同位素性质及其地质意义   总被引：2，自引：1，他引：2  

陈智超  陈斌田伟 《岩石学报》2007,23(2):295-306

太行山北段出露大规模中生代岩浆岩带,以中酸性岩为主,普遍含有基性微粒包体。锆石的SHRIMP U-Pb年代学研究表明,包体形成于126Ma左右,与寄主岩石大致同时形成。锆石的LA-MC-ICPMS Lu-Hf同位素原位测量研究表明,基性岩来自富集地幔的部分熔融,并遭受了一定程度的地壳混染;主要的中酸性岩基形成于壳幔岩浆混和过程,而岩基中微粒基性包体是经历分离结晶的基性岩浆注入酸性岩浆房中形成。  相似文献   

华北陆块早元古代基性岩墙群及其构造意义   总被引：1，自引：0，他引：1  

王岳军  彭头平  范蔚茗  赵国春  喻晓冰 《矿物岩石地球化学通报》2007,26(1):1-9

华北陆块中部带的晋冀蒙地区早元古代未变形变质基性岩脉形成于1781~1765 Ma。东部陆块鲁西地区早元古代类似的基性岩脉形成时间约为1841 Ma。中部带基性岩脉依据其FeOt含量、(Nb/La)N和(Th/Nb)N值的差异能划分为组1、组2和组3三类。它们的元素-同位素组成变化表明,组1样品起源于再循环大陆玄武质组分参与的交代岩石圈地幔,组2样品源于交代富铁岩石圈地幔与MORB组分的混杂源区,组3样品则是受辉长质组分混染的、经俯冲改造而成的岩石圈地幔产物。相反,鲁西地区基性岩脉亏损HFSE,具MORB型钕同位素组成。上述地球化学特征支持华北陆块中部带约1780 Ma的基性岩脉与早期俯冲碰撞作用的关系密切,而东部陆块约1840 Ma基性岩脉类似于弧后盆地构造背景产物。  相似文献   

湘赣地区中生代镁铁质岩浆作用与岩石圈伸展   总被引：53，自引：4，他引：53  

范蔚茗  王岳军  郭锋  彭头平 《地学前缘》2003,10(3):159-169

综合分析了华南内部中生代 (178～ 80Ma)镁铁质岩石的年代学和元素同位素地球化学特征。研究表明区内主要发育 4期镁铁质岩浆活动 :2 2 0Ma± ,175Ma± ,12 0～ 15 0Ma ,80～ 90Ma ,其中 2 2 0Ma仅在道县发育辉长岩包体。地球化学上区内 175Ma左右的宁远太阳山和赣中项家碱性玄武岩和 80～ 90Ma的镁铁质岩石主要表现为Hawaii OIB玄武岩的元素同位素地球化学特征 ,而175Ma的其他镁铁质岩石表现为岩石圈地幔属性。 12 0～ 15 0Ma的镁铁质岩石则介于岩石圈地幔端员与软流圈地幔端员之间。时、空上表现为以郴州—临武断裂为界 ,西侧自 170Ma左右的EMI型为主向 80～ 90Ma的OIB型为主迁移演化 ,而东侧则自老而新自EMII型 (175Ma)为主演变为以OIB型 (80～ 90Ma)为主。上述资料暗示区内至少存在 4期强烈的岩石圈减薄作用 ,软流圈物质上涌和岩石圈伸展减薄是华南中生代岩浆作用形成的主要机制。但 2 2 0Ma左右的伸展减薄范围局限 ,而较大规模的岩石圈伸展减薄和软流圈上涌始于 178Ma ,其形成可能与华南印支造山作用的后造山 (或后碰撞 )拉张裂解地球动力学背景有关。同时也暗示郴州—临武断裂可能是界定中生代EMI型扬子岩石圈和EMII型华夏岩石圈地幔的重要边界。  相似文献