简介:MarbleisassociatedwithultrahighpressureeclogiteintheDabieMountains.EastChina.U-Pbisotopedataforthemarbledefinea238U-206Pbisochronageof435±45awithaninitial206Pb/204Pbvalueof18.075±0.006,Theageof-435MaisinterpretedtorepresentthetimeoflimestonediagensisratherthanthetimeofmetarmorphicresettingaccompaniedbytheformationoftheultrahighpressureeclogitesatTriassic.ThepaleontologicandstratigraphicstudiesalsofavoralocalexcursioninthecarbonisotopiccompositionofthelatestordovicianwaterwithinasedimentarybasinbetweentheSino-KoreanandYangtzecratos.Becasusethelatestordovicianlimestonewasinvolvedintheeclogiteformation,thecontinentalcollisionbetweentheYangtzeandSino-KoreanPlateswouldpostdateordovican.
简介:Calculations,accordingtosomeopen-systemmodels,pointoutthatwhileastatisticallysignificantdiscrepancybetweentheresultsoftwoU-seriesmethods,^230Th/^234Uand^227Th/^220Th(or^231Pa/^235U),attestsarelativelyrecentandimportanturaniummigration,concordantdatescannotguaranteecloses-systembehaviorofsample.Theresultsof20fossilbonesfrom10Chinesesites,19ofwhicharedeterminedbytwoU-seriesmethods,aregiven,Judgingfromindependentagecontrols,8outofthe11concordantagesetsareunacceptable,Theresultsinthispapersuggestthaturaniummaycycleintooroutoffossilbones,suchgeochemicaleventsmaytakeplaceatanytimeandnoknownpreservingconditionmaysecurelyprotectthemfrombeingaffected.Soforthesitewwehavestudied,theU-seriesdatingoffossilbonesisoflimitedreliability.
简介:GlobalabruptclimatechangefromMarinoansnowballEarthtogreenhouseEarth,recordedascapcar-bonateoverlainondiamictite,hadshedthefirstlightonCambrianbio-radiation.Themostdocumentedcapcar-bonatesectionsaretypicalwithcomprehensiveδ13Cneg-ativevaluesandubiquitoussedimentarystructures,suchastepee-like,sheet-cracketc.,whichareassociatedwithsuccessiveglacialeustaticvariationcausedbyisostaticreboundinshallow-waterfacies.Herewereportadeep-waterbasinalcapcarbonatesectionwithstrongnegativeδ13CvaluesinthesouthernmarginoftheQinlingOrogen,Heyu,ChengkouCounty,ChongqinginChina,whichconsistsofmassivedolostonewithabundantcarbonaceouslaminae.However,itlacksthesedimentarystructureasmentionedaboveandisoverlainbythin-beddedsiliciousshalesandcherts.AK-bentonitebedwasdiscoveredwithinthebaseofcapcarbonates,about0.7mabovethetopoftheMarinoandiamictite.Magmaticzirconsthatweresep-aratedfromtheK-bentonitebedyieldaSIMSconcordiaU-Pbageof634.14-1.9Ma(lσ,MSWDcE=0.31,ProbabilityCE=1.000,n-=20).TheageisingoodagreementwithpreviouslyreportedTIMSU-PbagesfortheterminationofMarinoanglaciationandprovidesageochronologicalconstraintfortheEdiacaransuccessionsintheQinlingOrogen.
简介:Delaminationoccursmainlyinthelithosphericmantle,involvinginteractionwiththeasthenosphere,theprocessofwhichishardtoobservedirectly.ourresearchongranitoidsinthewesternkunlunorogenicbelt,China,indicatesthathighconterntsoftheheat-producingelementsThandUmayfurnishlithosphericdelaminationwithnewevidence,Atthesametime,wehaveestablishedtheTh-SiOandU-SiO2diagramstodiscriminatedelamination.
简介:TheYushugouterrainofhigh-pressuregranulitefaciesinsouthernTianshanMountainiscomposedmainlyofanophiolitesuite.Mostselectedziroconsareroundorellipticalinshape,andsomeareoftetragonalprismwithroundedges.Thegranulometricanalysesshowthattheyarewellsortedinsedimentation.ZrO2/HfO2ratiosinzirconsrangefrom45to57.thesecharacters,togetherwiththepetrologicandgeochemicalcharactersofplagioclase-garnet-orthopyroxenitebearingzircons,indicatethattheprotolithofplagioclase-garnet-orthopyroxenitemaybederivedmainlyfromvolcanicbasesurgesedimentarydebrisinoceanicislandsandfromclaysformedbyseafloorweathering.Zirconsaresimplyofpyroclasticdebris.Theophioliteformationageof(440±18)Maandthefirst-stagemetamorphicage(amphiboliteorgranulitefacies)of(364±5)Mawereobtainedwithamethodofmultiplegrainsindifferentgroupsandamethodofconcordiaplot.TheseagesprovideimportantinformationonthetemporalandspatialoccurrenceofsouthernPaleoxoicTianshanOcean,Thesubductionrateoftheoceaniccrustandtheformationmechanismofophioliteofgranulitefacies.
简介:本文利用胶质芽孢杆菌(Bacillusmucilaginosus)和黑曲霉(Aspergillusniger)处理铜-苯酚(简称铜-酚)和镉-苯酚(简称镉-酚)这类有机-无机复合污染模拟废水,采用胶质芽孢杆菌和黑曲霉分别单独、联合或先后处理等5种方式,探讨了这两类菌体对复合污染模拟废水的处理效果及优化方法。结果表明,微生物对铜-酚废水的处理效果优于对镉-酚废水。对于铜-酚废水的处理表明,当废水中苯酚浓度为50~200mg/L时,去除率可达80%以上,最高可达94.65%,其中铜的去除率较苯酚低;当模拟废水中铜浓度为30mg/L时,可达最高去除率(60.02%)。微生物对镉-酚废水的处理表明,当废水中镉离子浓度为4mg/L时,最高去除率为58.44%,苯酚的去除率一直保持在30%左右。
简介:林子宗火山岩事件是印度-亚洲大陆主碰撞过程的火山作用响应,对冈底斯带的构造演化具有重要意义。在冈底斯中段厅宫地区通过系统的LA-ICP-MS锆石U-Pb同位素测年,获得林子宗群典中组底部、年波组上部和帕那组顶部的火山岩锆石U-Pb年龄分别为(66.4±0.35)Ma、(53.6±1.5)Ma和(45±0.6)Ma。对林子宗火山岩的岩石地球化学分析表明,该火山岩具弧火山岩特征,早期表现出陆缘弧火山岩的特点,至中期年波旋回钾玄岩出现,标志着陆内岩浆作用的开始,到晚期帕那旋回则显示出陆壳重熔和地壳加厚的特征,记录了新特提斯洋消减俯冲到陆陆碰撞的地质信息。
简介:张三沟金矿区位于中亚兴蒙造山带东段,是该造山带上一个较为重要的金矿区,其研究程度较低.为厘定赋矿岩浆岩的成岩时代并限定其成矿时代,本文对主要赋矿的斜长花岗斑岩和宁远村组英安岩进行了锆石U-PbLA-ICP-MS同位素定年,获得其成岩年龄分别为106.2±1.2Ma和104.2±1.4Ma,说明二者可能是同期、同源岩浆在演化的不同阶段先后喷出和侵入的产物.早白垩世是东北地区乃至整个中国东部地区岩浆活动的高峰期,此时期区内爆发了大规模的成矿作用,张三沟金矿即为此期岩浆热液活动的产物.期间受太平洋板块俯冲作用的影响,区域上处于拉张伸展构造环境中,加厚岩石圈的拆沉作用导致软流圈上涌并发生底侵,最终形成同时期的广泛的岩浆活动并诱发大量的成矿作用.
简介:内蒙古边家大院银多金属矿床位于大兴安岭成矿带南段,是一个成因类型复杂的银多金属矿床.为了精确厘定该矿床的成岩时代,对区内与成矿关系密切的石英斑岩进行了LA-ICP-MS锆石U-Pb定年.结果表明,该斑岩的形成年龄为140±1.2Ma,为早白垩世岩浆活动的产物.岩石化学研究表明,边家大院石英斑岩的SiO2含量高(75.62%~75.80%),Al2O3含量较低(13.32%~13.33%),Alk质量分数较高(8.60%~8.71%),K2O/Na2O值为4.51~4.77.稀土配分曲线呈右倾轻稀土富集型,铕亏损强烈,δEu值为0.22.富集高场强元素Zr、Hf、Th和大离子亲石元素Rb、K,而亏损P、Ti、Sr、Ba、La.上述特征显示矿区石英斑岩与A1型非造山花岗岩一致,推断岩浆主要来源于地壳,形成于张性环境.结合矿床地质特征及前人在区域上的研究成果,认为燕山期是大兴安岭南段成矿和成岩高峰期之一,矿区石英斑岩形成的构造背景主要与古太平洋板块向西的大规模俯冲所引起的伸展作用有关.
简介:为探讨赣东北景德镇地区双桥山群的沉积时代与物质来源,对该区双桥山群安乐林组地层中发育的一套变火山碎屑凝灰岩夹层进行了年代学、地球化学及锆石Lu-Hf同位素研究。结果显示,该套火山碎屑凝灰岩的岩性主要为英安岩、安山岩,凝灰岩的LA-ICP-MS锆石U-Pb年龄为(809±2)Ma,表明该套岩石形成于新元古代。凝灰岩锆石的Hf同位素组成变化范围较广,其中二阶模式年龄为1426~2313Ma,主要集中于1.7~2.3Ga之间,其ε_(Hf)(t)均为负值-2.6~-16.5,t_(DM2)模式年龄远大于U-Pb年龄,表明该组岩石的岩浆来源于元古代地壳物质的再循环。