简介:本文重点研究了大别山潜山,牌楼地区榴辉岩P-T-t轨迹,探讨了大别山地区榴辉岩成因,认为榴辉岩原岩主要是碱性玄武岩,少部分洋脊拉斑玄武岩岩浆早期结晶分异堆晶岩及部分钙质沉积岩。它们在华北与杨子板块碰撞时(260±30Ma),地壳向下俯冲到40-60km处,温度550°-830°C,压力1.1-2.1GPa的条件下形成的。在构造抬升过程中,榴辉岩产生了角闪岩相、绿片岩相退变质作用,角闪岩相温压条件:460°-570℃,0.4-0.7GPa。流体包裹体研究表明:流体包体成分主要为NaCl-H_2O,H_2O,NaCl-CO_2-H_2O体系,变质作用过程从早至晚由氧化向还原环境转化。熔融包体的发现表明:榴辉岩形成具有局部深熔作用。从榴辉岩产状、岩石化学、地球化学特征表明本地区榴辉岩不是一种成因,同时具有B类、C类榴辉岩特征。
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简介:WhileattendanceatpreviousIGC'swasremarkable,themorethan7,000earthscientists,exhibitorsandguestswhometinFlorenceforthe32^ndInternationalGeologicalCongresssetanall-timerecordasthehighestnumberofparticipants.Theycamefrom120countriesand75%werenotItalian.Thisproportionofforeignattendeeswasthelargestever;inlinewithatrendofincreasingnonlocalparticipation,ittestifiestothevitalityandinternationalcharacteroftheIGCs.
简介:ThereareobviousdifferencesinthemineralassemblageandmetamorphicP-TconditionsbetweentheeclogitesfromthenorthernandsouthernpartsoftheeasternDabieMountains.ThosefromthenorthernpartofthemountainsaredevelopedinAlpineperidotiteandgneiss.Theyhaveamineralassemblageofgarnet+diopsidewithnoquartz,andwereformedattemperaturesof600℃-740℃.Thosefromthesouthernpartaredevelopedingneissandmarble.Theyconsistofgarnet+omphacite+lessquartzandweremetamorphosedattemperaturesintherangeof650°-800℃.Thesedifferencessuggestthattheformermaybeformedduringthemetamorphismofthedeepsubductedoceaniccrust,whereasthelattermaybegeneticallyrelatedtothesubductionofthecontinentalcrustinthisarea.
简介:KarstrocksfromtheHuanglongFormationexposedatthemarginoftheEasternSichuanBasincanbedividedintofourtypes:slightlycorroded,moderatelycorrodedporous,intenselycorrodedbrecciatedandintenselycorrodedandreplacedsecondarycalcickarsticrocks.Thecarbon,oxygenandstrontiumisotopecompositionsofthevariouskarstrocksareanalyzedsystematicallyandcomparedtorockswithoutkarstcorrosion.Theresultsindicatethat(1)theHuanglongFormationintheeasternSichuanBasinwasarestrictedbaysuppliedandcontrolledbyfreshwaterinwhichmudmicriteandmud-dolomicriteexhibitlowδ13Candδ18Ovaluesandhigh87Sr/86Srratios;(2)alltypesofkarsticrocksinthepaleokarstreservoirsoftheHuanglongFormationintheresearchareaareaffectedbyatmosphericfreshwaterwiththeδ13Candδ18Ovaluesand87Sr/86Srratiosintheoriginalformationapproachingthoseofatmosphericfreshwater,whichreflectsancienthydrologicalconditions,fluidproperties,isotopicsourceandthefractionationeffect;(3)theintenselycorrodedandreplacedsecondarylimestoneisaffectedbyavarietyofdiageneticfluids,oftenreflectedbyδ13Candδ18Ovalues,whilethe87Sr/86Srratiosexhibitthestrongdegreeofthecorrosion;(4)aftercomparingthe87Sr/86Srratiosofeachtypeofkarstrock,thediageneticfluidsaredeterminedtobemainlyatmosphericfreshwater,anddependingonthestrengthofcorrosion,andthelow87Sr/86Srratiofluidsinthelayerwillparticipateinthekarstprocess.Thecarbon,oxygen,andstrontiumisotopesofdifferentkarsticreservoirscanprovidemeaningfulgeochemicalinformationforforecastingandevaluatingthedevelopmentanddistributionrulesoftheHuanglongFormationatthemarginoftheeasternSichuanBasinintimeandspace.更多还原
简介:新疆哈密东天山构造岩浆带位于尾亚-罗布庄磁力高带上的喀拉塔格磁场小区,该带发育幅值在200~300nT的正磁场区,封闭磁异常对应于石炭纪石英闪长岩或隐伏基性侵入岩体。钳子山C07-2磁异常为该区带高磁异常,最高幅值2340nT。经钻探验证,打出3层低品位含铜钛磁铁矿,总厚119m。据81个化学样分析,TFe约3.6%~28.80%,平均品位13.5%,TiO21.31%~2.33%。ZK0701-10/5层(111~113m)见有2m厚具工业品位的铜矿体和磁铁矿体,分析结果为Cu0.4%,TFe28.8%。该钻探成果为在哈密玉西地区寻找岩浆型钛磁铁矿提供了有力依据。
简介:在华南的Dajiangbian形成是统治siliciclastic的沉积继任,低档变态在卡赛西亚·布洛克的西方的边缘上扔了,并且被glaciogenicdiamictite(Sizhoushan形成)盖住。Sizhoushanglaciogenic阶层能被归因于Jiangkou冰川(Sturtian冰川)他们在华南与Jiangkou阶层分享stratigraphic和lithological类似的事件。在整个Dajiangbian形成的上面的部分的一些碳酸盐,燧石和页岩单位为碳酸盐碳同位素被取样(13Ccarb)和器官的碳同位素(13Corg)分析。geochemical的一个范围索引包括氧同位素(18O)并且Mn/Sr(Fe/Sr)比率建议主要的碳同位素价值在上面的Dajiangbian形成被保存。上面的Dajiangbian形成表演13C向上减少向的-0.1,的carb到-5.4。我们建议否定13在Sizhoushandiamictite下面的C旅行是有Pre-SturtianIslay13Ccarb异例并且与全球Neoproterozoic同位素地层学允许关联。我们发现碳酸盐和上面的Dajiangbian形成的器官的碳同位素数据被联合,与13Ccarb-13C在多重大陆上观察的org模式。
简介:TheTan-LufaultzonejoinstheDabieMountainsonitseasternmargin,andoffsetstheDabieandSuluorogenicbeltssinistrallyforabout500km.Onthebasisofcalculationoftemperatureandpressureexperiencedbythetwophasesofthefaultzoneaswellasthethermo-chronologicalinformationonmylonitefromtheearlierandlaterTan-LufaultzonesontheeasternmarginoftheDabieMountains,thispaperdiscussesthedelaminationhistoryandupliftingmagnitudesoftheDabieMountainsfromearlierJurassictoearlierCretaceous.Frommineralassemblages,mineraldeformationandmuscovite-chloritegeothermometrycalculation,itisknownthatthetemperatureexperiencedbythetwophasesofTan-Lufaultzonesarebetween400℃and450℃,andtheconfiningpressuresarebetween0.25Gpaand0.36GPafortheearliershearzonesand0.24-0.39GPaforthelateshearzones.AccordingtothegeobarometryofSi-in-phengiteandbyconsideringshearheatingandtectonicover-pressure,itisconcludedthatthemaximumformationdepthsforthetwophasesoftheductileshearzonesarenotmorethan12km.Differentialformationdepthsforthetwophasesofshearzonesare1-2kmatmost.Atabout190Maand128Ma,theTan-Lufaultzoneexperiencedtwophasesofcoolingevents.Duringthisperiod,theeasternmarginoftheDabieMountainsexperiencedatectoniccalmperiodandnouplifting.AccordingtoinformationfromtheTan-Lufaultzone,theupliftingmagnitudesoftheDabieorogenicbeltsarenotmorethan12kmduringtheearlierCretaceous.