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白云岩成因探讨:新疆三塘湖盆地发现二叠系湖相喷流型热水白云岩 总被引:18,自引:2,他引:16
晚石炭世—早二叠世是新疆北部地区构造转换、海陆变迁的重要变革时期,包括三塘湖盆地在内的北疆地区该时期发育多个呈近东西向分布的陆内裂谷,其中存在大量基性、酸性及中性火山岩,它们以裂隙式喷发为特征。中二叠世芦草沟期,北疆地区发育裂谷期后半深湖沉积,沉积了厚层暗色泥岩、凝灰质泥岩、白云质泥岩夹白云质泥晶灰岩、凝灰岩、白云岩及火山岩的岩石组合,在暗色泥岩、凝灰质泥岩中普遍发育吐鲁番鳕鱼、双壳、叶肢介、介形虫等化石。其中的白云岩具如下特征:以铁白云石为主,多呈泥晶和粉晶状,与泥晶石英和有机质(含藻类)构成纹层;与方沸石岩互层,并作为方沸石的胶结物同时交代方沸石;伴生纳长石、伊利石、硬石膏、黄铁矿等多种热液矿物。此类白云岩及其热液矿物为本研究区首次发现,其分布与上石炭统火山岩的分布范围一致,表现出裂隙式、点式分布特点;火山岩中发育丰富的网状、树枝状裂缝并被热液矿物充填,可见火山岩具角砾状构造,可能反映了热液喷流口的沉积特征。初步分析认为该白云岩是一种与岩浆作用、深部热液作用相关的喷流型湖相热水沉积白云岩。 相似文献
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北半球中高纬度大气环流主模态的季节演变及其与北极海冰变化的联系 总被引:2,自引:0,他引:2
利用31a(1979—2009)气候月平均的海平面气压(SLP)资料,提出1种与北半球中高纬度环流转变相适应的分季法。并根据这个客观分季方法,通过SEOF分析,发现大气环流主模态的季节演变有着典型的北极涛动(AO)空间结构,其时间系数在1990年代中期发生转型。500hPa上纬向波的涡度有着南北反位相的分布特征,冬季正涡度的区域对应着气旋性环流,其覆盖范围广,而夏季正涡度区域更偏北,可见AO在冬季增强,夏季减弱。北半球SLP异常的EOF分解第一模态为北极涛动(AO),第二模态是偶极异常(DA);将这2个模态称之为北半球中高纬度大气环流异常的优势模态。通过计算优势模态与海冰面积的超前滞后相关性,发现AO依然是控制海冰变化的前期大气环流异常的模态,而DA则可能是海冰快速变化后期大气环流的主导模态。 相似文献
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INCONSECUTIVE “SANDWICH STRUCTURE” PATTERN FOR HIGH TEMPERATURE WARM WATER IN THE WESTERN PACIFIC WARM POOL 总被引:1,自引:1,他引:0
An inconsecutive high frequency distribution with a"sandwich structure"pattern for high temperature warm water warmer than 29℃ in the western Pacific warm pool(WPWP) was found using Tropical Rainfall Measuring Mission(TRMM) sea surface temperature(SST) data,a relatively high resolution data for space.This phenomenon only shows up in boreal summer(June to September),and becomes obvious when WPWP SST is higher than 29℃.As observed,East Asian summer monsoon(EASM) impinges on Philippine Islands in July,which has an important impact on the formation and maintenance of the "sandwich structure".Winds affect the distribution of SST in two ways:one by increasing the local latent heat flux and the other by transporting cold water towards the southeast of Philippine Islands. 相似文献
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北极放大的时空变化特征及其与北极涛动的联系 总被引:1,自引:1,他引:0
The Arctic near-surface air temperatures are increasing more than twice as fast as the global average–a feature known as Arctic amplification(AA).A modified AA index is constructed in this paper to emphasize the contrast of warming rate between polar and mid-latitude regions,as well as the spatial and temporal characteristics of AA and their influence on atmospheric circulation over the Northern Hemisphere.Results show that AA has a pronounced annual cycle.The positive or negative phase activities are the strongest in autumn and winter,the weakest in summer.After experiencing a remarkable decadal shift from negative to positive phase in the early global warming hiatus period,the AA has entered into a state of being enlarged continuously,and the decadal regime shift of AA in about 2002 is affected mainly by decadal shift in autumn.In terms of spatial distribution,AA has maximum warming near the surface in almost all seasons except in summer.Poleward of 20°N,AA in autumn has a significant influence on the atmospheric circulation in the following winter.The reason may be that the autumn AA increases the amplitude of planetary waves,slows the wave speeds and weakens upper-level zonal winds through the thermal wind relation,thus influencing surface air temperature in the following winter.The AA correlates to negative phase of the Arctic oscillation(AO) and leads AO by 0–3 months within the period 1979–2002.However,weaker relationship between them is indistinctive after the decadal shift of AA. 相似文献
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新疆三塘湖地区石炭纪火山岩年代学、地球化学及其大地构造意义 总被引:3,自引:0,他引:3
三塘湖地区石炭纪火山岩出露于新疆准噶尔盆地东北缘考克赛尔盖山、三塘湖乡、大黑山及淖毛湖一带,位于克拉美丽断裂带北侧.主要岩石组合为基性、中酸性熔岩及火山碎屑岩.岩石地球化学研究显示基性-中酸性火山岩为同源岩浆产物,其中的玄武岩样品富集大离子亲石元素(LILE),相对亏损高场强元素(HFSE),具有明显的Nb-Ta-Ti负异常.石炭系火山岩源于亏损地幔,岩浆在上升过程中未曾受到地壳物质的混染,并经历了岩浆结晶分异作用过程.综合地层岩石组合、岩石地球化学研究,认为三塘湖石炭系火山岩应形成于与俯冲作用有关的构造环境.利用锆石U-PbLA-ICPMS获得安山岩的锆石U-Pb同位素年龄(328.9±1.9)~(331.3±2.3)Ma,该年龄代表了安山岩的成岩年龄.结合区域内的地质记录、同位素年代学资料的综合分析研究,表明准噶尔洋北缘的俯冲消减作用在早石炭世已经存在,三塘湖火山岩形成于准噶尔洋早石炭世俯冲作用诱发的岛弧岩浆作用. 相似文献