中国东部燕山期大规模岩浆活动与岩石圈减薄:与大火成岩省的关系   总被引：36，自引：4，他引：32       下载免费PDF全文

张旗  金惟俊  李承东  王元龙 《地学前缘》2009,16(2):21

论述了大规模岩浆活动与岩石圈减薄的关系,指出软流圈地幔与地壳直接接触时,即岩石圈最大减薄时(岩石圈地幔厚度为0),岩石圈厚度等于地壳厚度。中国东部岩石圈最大减薄的时间在燕山期,在这之前和之后,岩石圈是厚的。讨论了中国东部大规模岩浆活动与板块俯冲的关系,认为中国东部燕山期岩浆活动与太平洋板块没有关系:中国东部不属于环太平洋构造带,不是安第斯型活动陆缘,中生代玄武岩不具有岛弧玄武岩的特征,从中酸性岩浆岩得不出岛弧的结论,从三叠纪开始的古太平洋板块扩张方向的演变也不支持板块向西俯冲的认识。认为中国东部燕山期大规模岩浆活动可能与超级地幔柱的活动有关,是一种新的大火成岩省类型。文中将大火成岩省分为两类:一类为B型大火成岩省,部分熔融发生在岩石圈底部,以发育玄武岩为特征;另一类为G型大火成岩省,部分熔融发生在下地壳底部,以发育大规模花岗质岩浆为特征。根据中国东部大规模岩浆活动的时空分布分出5个大火成岩省:鄂霍茨克(大兴安岭北端)、张广才岭—小兴安岭、华北—大兴安岭、华南和东部沿海大火成岩省。认为岩石圈减薄可以产生多种效应,是地壳演化的最重要的动力学因素,但唯独与地壳浅部的伸展事件无关。还评论了流行的岩石圈减薄的见解,认为流行的见解将岩石圈减薄定位在新生代(岩石圈厚80～120km)是似是而非的,不是科学的命题。  相似文献   

千岛湖叶绿素a的时空分布及其与影响因子的相关分析   总被引：11，自引：6，他引：5  

李培培  史文  刘其根  余元龙  何光喜  陈来生  任丽萍  洪荣华 《湖泊科学》2011,23(4):568-574

为了解千岛湖在大量放养鲢鳙鱼后叶绿素a的时空分布格局及其与主要环境因子的相关性,本文于2007年1月至2009年12月对千岛湖叶绿素a及其他10个水质理化指标进行了每月定期采样及监测.结果表明:上游河流区和过渡区叶绿素a含量存在明显的季节变化,其共同特点是每年会形成春季和夏末秋初的双高峰.叶绿素a含量在空间分布上具有一...  相似文献   

川东-武陵构造带下古生界海相页岩构造变形特征及对页岩气保存的影响     

李春麟  李小诗  王宗秀  梁明亮  张凯逊  谭元隆  陶涛  高莉 《地质力学学报》2020,26(6):819-829

川东-武陵构造带下古生界发育的两套海相页岩层系(下寒武统牛蹄塘组和上奥陶统五峰组—下志留统龙马溪组)不仅是区域内重要的滑脱层,也是页岩气勘探开发的重点层位。通过野外详细的构造解析及室内显微观察,从宏观露头—显微尺度分析了页岩的变形特征,认为页岩至少存在两期构造变形:早期顺层向北西或南东的逆冲和晚期的切层断层作用。页岩的变形强度随着与断裂带距离的变化而发生改变,远离断裂带的地区页岩变形主要表现为近直立的微裂隙,属脆性域;靠近断裂带,页岩的变形特征逐渐表现为脆-韧性过渡,开始发育糜棱化构造;在断裂带内部,页岩强烈面理化,发育大量的糜棱化构造,属韧性域。通过氩离子抛光和扫描电镜技术,分析了变形页岩内部的孔隙演化特征,认为随着变形作用从脆性—脆-韧性过渡—韧性的转变,页岩内部的孔隙类型不仅可以发生转换,而且页岩内部孔隙的大小、分布特征也随之改变。在此基础上,进一步讨论了中国南方复杂构造区下古生界页岩变形对页岩气保存的影响,认为顺层剪切滑脱作用会改变页岩内部的孔隙体系,有利于页岩气的富集;切层的伸展或走滑剪切作用不仅会破坏先前形成的油气圈闭,而且会导致油气沿着断裂带从高势区向低势区运移,进而造成油气散失。   相似文献   

Dinomischus from the Middle Cambrian Kaili Biota, Guizhou, China   总被引：2，自引：0，他引：2  

PENG Jin ZHAO Yuanlong LIN Jih-Pai 《《地质学报》英文版》2006,80(4):498-501

Dinomischus is a rare solitary epifaunal suspension feeder. The over-all morphology of Dinomischus consists of a conical calyx surrounded with elongate bracts and an elongate stem. Visceral mass and stomach sac are evident in the body cavity. Dinomischus is interpreted as a primative ancestor of living entoprocts based on similarities in morphology and mode of life. Previously, Dinomischus is only known in two localities： the mid-Middle Cambrian Burgess Shale Biota and the Early Cambrian Chengjiang Biota. A single specimen of Dinomischus cf. D. isolatus Cowry Morris, 1977 from the Kaili Biota, Guizhou, China is reported here. The discovery of Dinomischus in the Kaili Biota extends its geographical range and indicated that the rare Dinomischus could tolerate deeper water settings during the Middle Cambrian.  相似文献   

Geochemistry of the trace elements and rare-earth elements at the boundary between Cambrian Series 2 and Series 3 at Jianshan, South China: Paleoenvironmental and stratigraphic implications     

Xinglian Yang  Yuanlong Zhao  Qingjun Guo  Hong Yang 《中国地球化学学报》2012,31(4):465-475

The Jianshan section in Jianhe County,Guizhou Province,is a very important auxiliary section to the candidate stratotype at the boundary between Cambrian Series 2 and Series 3.Twenty four samples collected from the Jianshan section of the Kaili Formation were analyzed for the concentrations of trace element and rare-earth elements(REEs) by inductively coupled plasma mass spectrometry.The trace element and REE geochemical characteristics of the Kaili Formation at the Jianshan section show that trace element composition and REE distribution patterns across the section are covariant.Notably,at 44 m above the base of the Kaili Formation,most trace element contents and REEs concentrations are lower than those values observed below 44 m.Above 44 m,an increasing trend in the concentration of both trace elements and REEs is observed.These geochemical data indicate important,but subtle,changes at the 44 m horizon.If this is,in fact,verified by work in progress,geochemical criteria can provide additional supports for defining the top surface of Cambrian Series 2,especially in sections where Oryctocephalus indicus is absent.Trace element ratios,specifically Ni/Co,V/Cr,V/(Ni+V) and Th/U as well as Ce and Eu anomalies indicate that the sedimentary environment of the Kaili Formation at the Jianshan section was oxidizing,that benthic redox conditions were less oxic,and may have been influenced by freshwater as compared to the Balang area.Moreover,the Eu anomalies observed in the Kaili Formation are similar to the negative Eu anomalies observed in post-Archean sedimentary rocks,and reveal fluctuations in oxygen content from the bottom to the top of the Kaili Formation.  相似文献   

埃迪卡拉纪印痕化石是陡山沱期 宏体藻类的固着器吗？ ——Hiemalora与Gesinella的对比研究     

唐烽  金幸生  王约  丁明  赵元龙  高林志 《地质论评》2014,60(5):1009-1018

Hiemalora是一类广为分布的埃迪卡拉(Ediacaran)纪(震旦纪)圆盘状印痕化石,周围具流苏状或触须状突起,曾被解释为似水母动物,或某种叶状生物的固着器官,但以往罕见其与叶状生物体共同保存。本文报道了华南贵州震旦纪陡山沱组一类保存完好丰富的被确认为藻类的碳膜化石——革辛娜藻Gesinella,具有完整的须状固着构造。这一须状构造的形态和大小与Hiemalora非常相似,致密加厚的基部及其周围辐射状分布的丝状或须根状构造,可以分别和后者的中央盘以及周缘突起的"触须"相比较。陡山沱组的这一类碳膜化石同时保存有明显巨大的形同藻类的叶片和固着器,为研究埃迪卡拉生物群的底栖印痕化石提供了新的认识,即:盘状的Hiemalora可能是多细胞藻类的固着器官,而不一定是最初解释的似水母动物或其它叶状体生物的固着构造。不过,证实这一点尚需更进一步地研究埃迪卡拉纪生物的保存方式和埋藏环境。  相似文献   

Thermohaline finestructure observed near the northern Philippine coast     

王凡  李元龙 《中国海洋湖沼学报》2012,30(6):1033-1044

Using hydrographic measurements from three recent surveys in the western tropical Pacific, this study revealed the existence and general features of thermohaline finestructure near the northern Philippine coast. Pronounced finestructures were detected in the layers of the North Pacific Tropical Water (NPTW) and the North Pacific Intermediate Water (NPIW) during all three cruises and shown to be mainly thermohaline intrusions. Characteristics of the intrusions were further investigated with spiciness curvature and salinity anomaly methods. The vertical scale of the intrusions was 20-50m and 50-100m in the NPTW and NPIW layers, respectively. Within the NPTW layer, the Turner angle distribution and correlation between salinity and density anomalies suggested that diffusive convection between surface fresh water and subsurface saline water played an important role in the development and maintenance of the intrusions. In addition, connection between thermohaline finestructure and larger-scale oceanic processes was explored using historical hydrographic data. The results reveal that the salinity field and the distribution of the intrusions in this region were largely determined by mesoscale eddies. As a result of eddy stirring, both isopycnal and diapycnal temperature/salinity gradients were strengthened, which gave rise to the development of thermohaline intrusions. The intrusions acted to enhance heat and salt fluxes and resulted in the mixing of water masses being more efficient. By linking mesoscale eddy stirring to micro-scale diffusion, thermohaline finestructure plays a vital role in the ocean energy cascade and water mass conversion in the northern Philippine Sea.  相似文献   

Energetics and temporal variability of internal tides in Luzon Strait: a nonhydrostatic numerical simulation     

������  ��һ��  ��Ԫ��  ���� 《中国海洋湖沼学报》2012,30(5):852-867

A fully nonlinear,three-dimensional nonhydrostatic model driven by four principal tidal constituents(M2,S2,K1,and O1) is used to investigate the spatial-temporal characteristics and energetics of internal tides in Luzon Strait(LS).The model results show that,during spring(neap) tides,about 64(47) GW(1 GW=109 W) of barotropic tidal energy is consumed in LS,of which 59.0%(50.5%) is converted to baroclinic tides.About 22(11) GW of the derived baroclinic energy flux subsequently passes from LS,among which 50.9%(54.3%) flows westward into the South China Sea(SCS) and 45.0%(39.7%) eastward into the Pacific Ocean,and the remaining 16(13) GW is lost locally owing to dissipation and convection.It is revealed that generation areas of internal tides vary with the spring and neap tide,indicating different source areas for internal solitary waves in the northern SCS.The region around the Batan Islands is the most important generation region of internal tides during both spring and neap tides.In addition,the baroclinic tidal energy has pronounced seasonal variability.Both the total energy transferred from barotropic tides to baroclinic tides and the baroclinic energy flux flowing out of LS are the highest in summer and lowest in winter.  相似文献   

Thermohaline intrusions in the thermocline of the western tropical Pacific Ocean     

LI Yuanlong  WANG Fan 《海洋学报(英文版)》2013,32(7):47-56

The existing high-resolution hydrographic data in the western tropical Pacilit; Ocean are used to explore the spatial distribution and primary characteristics of thermohaline intrusions in the thermocline. Statistics show that the vertical scales of intrusions are 20-40 m in the upper thermocline （22.0-26.0δ0） and 40-80 m in the lower thermocline （26.0-27.2δ0）. In the upper thermocline, the most intensive intrusions exist at the equatorial front （EF） where north/sonth Pacilic water masses converge, anti Ihe westward spreading of the north Pacilic tropical waler （NPTW） in the Philippines Sea also produces patches of intrusions surrounding its high-salinity tongue. In the lower thermocline, intrusions are also strong at the tropical front （TF） which is the boundary between the north Pacilic subtropical/tropical waters. At the bottom of the thermocline （at about 27.0δ0）, intrusions mainly exist near the western boundary, which are produced by intermediate water convergence through the advection of subthermocline western boundary Ilows. Most strikingly a ＂C＂-shape distribution of intrusions at around 26.4δ0 is revealed, covering the vicinity of the EF the TE and the Mindanao Current （MC）, i.e., tile western boundary pathway ol the norlh Pacilic subtrnpical cell （STC）. Synoptic section analysis reveals that intrusions are more prominent on the warm/sally flank ot the fronts, implying more cross-front tongues of cold/fresh water. Among the intrusions, those at the EF are of best lateral coherence which implies a unique driving mechanism involving near-inertial velocity perturbations near the equator.  相似文献   

贵州台江凯里生物群中遗迹化石（Gordia）与水母状化石（Pararotadiscus）的关系及其意义   总被引：4，自引：2，他引：4  

王约赵元龙  林日白王萍丽 《地质论评》2004,50(2):113-119,i001,i002

贵州台江凯里生物群中的遗迹化石Gordia marina Emmons常被保存在水母状化石Pararotadiscus guizhouensis Zhao and Zhu盘体的上下，构成凯里生物群生态特色之一。笔者认为，G．marina可能系蠕形类造迹动物在层面或近层面觅食或吞食富含有机物的沉积物所形成。生活于清澈陆棚环境一定水域的P.guizhouensis，由于突发性快速沉积事件的发生，改变了海水的物化条件，而被“毒死”，并随沉积物安静地沉落于弱氧化-还原环境的海底。在较为缓慢的腐烂过程中，营食沉积物的G．marina造迹生物觅食于P.guizhouensis盘体上下富含有机物的沉积物中。随着沉积物的增厚，P．guizhouensis生物尸体周围的微环境还原性增强，腐烂过程很快被终止，P．guizhouensis生物软体得以保存，浅层或层面觅食性造迹生物亦随即离去，留下其生活活动的潜穴。同时通过研究，还认为G．molassicd(Heer)与G．marina为同义名，可能为G．marina造迹生物的幼体。  相似文献