岩石学报杂志 SCI期刊 北大期刊 CSCD期刊 统计源期刊

岩石学报 2009年第12期杂志 文档列表

西秦岭与埃达克岩和喜马拉雅型花岗岩有关的金铜成矿及找矿问题-

摘要：秦岭金矿分布广,目前学术界大多认为分属于造山型和卡林型金矿两类.该区印支期花岗岩发育,大多具有埃达克岩和喜马拉雅型花岗岩(低Sr和Yb)的特点,与金铜矿在时空分布上相关.美国内华达州卡林型金矿是世界级的金矿聚集区.与卡林型金矿有关的第三纪岩浆岩(中酸性火山岩和浅成花岗岩)也具有埃达克岩和喜马拉雅型花岗岩的地球化学特征,暗示内华达卡林型金矿也来源于加厚下地壳的底部.本文讨论了埃达克岩和喜马拉雅型花岗岩有利于成矿的机理,并根据西秦岭金矿与花岗岩分布的关系,提出以夏河-宕昌-两当-凤县为界将西秦岭划分为南北两个成矿区和13个成矿聚集区:北区花岗岩发育,有利于寻找斑岩型、夕卡岩型等热液型金铜矿床;南带侵入岩少而小,有利于寻找远离岩体的金矿(包括卡林型等).鉴于西秦岭印支期埃迭克岩和喜马拉雅型花岗岩发育,金铜尤其是金矿分布多,储量大,且大多与埃达克岩或喜马拉雅型花岗岩有关,可能是中国金矿最具潜力的地区,有利于特大型金铜矿的产出,可能发展成为中国最大的金矿聚集区.为此,建议加强本区花岗岩与金铜成矿关系的研究,革新找矿思路和找矿技术方法,以实现找矿的新突破. Abstract： Gold deposits spreading extensively in west Qinling have been grouped into such two types as orogenic type and Carlin type, which is accepted by most researchers of the present academic field. In the study area developed Indo-chinese epoch granite, most of which have the characteristics of adakite and Himalayan type granite (relatively low content of Sr and Yb), and related to distribution of gold and copper deposits spatially and timely. The study on Carlin type gold deposits in Nevada, USA show that it is a world-level concentration area of gold deposit, Tertiary igneous rock (intermediate-acid rock and hypabyssal granite) related to gold and copper deposits have the

锡林浩特杂岩和蓝片岩的锆石U-Pb年代学及其对索仑缝合带演化的意义-

摘要：报道了内蒙索仑缝合带附近的锡林浩特杂岩和苏左旗混杂带中蓝片岩块的锆石U-Pb年代学数据.锡林浩特杂岩中碎屑锆石来源复杂,从晚太古至晚古生代均有.最年轻的碎屑锆石U-Pb年龄为280～340Ma,与该区最年轻的弧岩浆岩年龄一致,表明该杂岩的原岩最终形成于晚古生代,而不是前寒武陆块残留.锡林浩特杂岩原岩的沉积源区主要是古生代的孤岩浆岩和部分裸露的前寒武陆壳,可能是弧前沉积建造.蓝片岩的锆石U-Pb年龄为318±5Ma(范围338～280Ma),这些锆石显示典型岩浆振荡环带结构,因此该年龄可能代表其原岩形成年龄,而其变质应该在280Ma之后.所以,锡林浩特杂岩和混杂带中蓝片岩块的变质变形作用可能发生在晚二叠,与索仑缝合带强烈的弧陆碰撞有关,暗示索仑缝合带的碰撞缝合时间在晚二叠,而不是许多人坚持的泥盆纪. Abstract： We report the zircon U-Ph age data for the Xlinhot metamorphic complex and the blueschist block from a melange belt (south Sonidzuoqi) along the Solonker suture zone, Inner Mongolia. Detrital zircons from the Xilinhot complex have complicated origins, with U-Pb ages ranging from Late Archean to Late Paleozoic times. A few zircon grains show U-Pb age in the range 280 -340Ma, identical to those of the youngest arc magmas from Sonidzuoqi and the northern north China craton. This suggests that formation of the protolith of the Xilinhot complex was finally completed in the Late Paleozoic, rather than in Precambrian times. The protolith of the Xilinhot complex probably represented forearc sediments. Zircons from the blueschist show U-Pb ages in the range 338 ～ 280Ma, with a mean ~(206)Pb/~(238)U age of 318±5Ma. These zircons show oscillatory and sector-zoning, typical of magmatic origin; thus the age probably represents the formation age of the protolith of bluschist, and the metamorphism could occur later than 280Ma. Therefore, the Xilinhot complex and blueschist formed likely i

济阳盆地南缘古近系碎屑高压变质矿物的发现及其构造古地理含义-

摘要：针对华北济阳盆地南缘、鲁西隆起北麓的博兴洼陷新生代沉积,通过矿物分离、显微鉴定、探针分析与计算,发现古近系孔店组和沙河街组第四段中存在确凿的碎屑蓝闪石、冻蓝闪石、多硅白云母等高压矿物.结合同层位碎屑重矿物组合与区域碰撞造山带物源的对比分析,说明上述高压矿物源于胶东地区的苏鲁造山带,而其源岩是否与俯冲洋壳的折返有关值得进一步研究.对碎屑蓝闪石等高压矿物物源进一步的讨论说明,它们极可能直接来源于苏鲁造山带,但不排除博兴洼陷同时期也接受了来自鲁西地区的剥露物质(含再旋回物源).因此,鲁西隆起-苏鲁造山带晚中生代-古近纪早期具有明显的东高西低的古地理特点,而自古近纪始新世中期45Ma左右(相当于沙河街组四段顶界年龄)古地势开始逆转.换句话说,45Ma以后鲁西隆起基本阻隔了直接来自苏鲁造山带的物源. Abstract： Through detrital heavy mineral separation, microscopic identification and probe measure and compositional data analysis, some detrital high-pressure metamorphic minerals, including glaucophane, barroisite and phengite, were found from the Kongdian Formation and the No. 4 segment of Shahejie Formation, Paleogene, in the Boxing Sag located in the south margin of Jiyang basin near the north foot of Luxi Uplift. Provenance correlation analysis, with depositional records of detrital heavy mineral assemblages and petrologic tectonic attributes of regional collisional orogenic belts, shows that the detrital high-pressure minerals sourced from the Sulu orogenic belt, in which high-pressure metamorphic rocks probably resulted from return of deep subducted oceanic crust (more research proofs needed). Further discussion on provenances of detrital high-pressure minerals in the Boxing Sag most probably directly sourced from the Sulu orogenic belt during the Early Paleogene. At the same time, exhumation materials (including recycled deposit

越南西北部Posen花岗岩锆石U-Pb年龄和Hf同位素组成特征-

摘要：本文报道出露于越南西北部的Posen花岗岩岩体锆石U-Pb年龄和Hf同位素组成特征,讨论岩石成因和该地区新元古代岩浆作用的大地构造意义.分析3个花岗岩样品获得723Ma至760Ma的锆石U-Pb年龄,表明花岗岩形成于新元古代.该花岗岩的锆石Hf同位素组成有较大的变化范围,ε_(Hf)(t)值变化范围为-16.1至+3.4,单阶段Hf模式年龄为1186～1945Ma,暗示Posen花岗岩有着复杂的源区物源组成.在误差范围内,锆石两阶段Hf同位素模式年龄值主要集中在2.0～2.1Ga,与两阶段Nd同位素模式年龄值2.1～2.2Ga一致,说明花岗岩体主要由古元古代地壳物质部分熔融形成的.部分锆石颗粒具有正ε_(Hf)(t)值,可能指示花岗岩岩浆形成过程中存在壳-幔混合相互作用.在越南西北部发育新元古代岩浆作用可能与扬子板块广泛发育的、伴随Rodinia超大陆裂解过程的岩浆活动存在成因的联系,也揭示越南西北部地体可能与扬子板块具有亲缘关系,因此,可以推断马江断裂带应该代表印支板块和华南板块之间的古特提斯缝合带在越南西北部的延伸. Abstract： This study presents zircon U-Pb ages and Hf isotopic composition of the Posen granite exposing in northwestern Vietnam and discusses its petrogenesis and tectonic significances of the study area in Neoproterozoic. Zircons from three samples of the Posen granite were analyzed and yield U-Pb ages of 723Ma to 760Ma, suggesting that the granite formed in Neoproterozoic. Zircon grains from this granite exhibit variable Hf isotopic compositions, their ε_(Hf)(t) values range from -16.1 to +3.4, single-stage Hf modal age values from 1186Ma to 1945Ma, implying complex material sources for the magma of this granite. Two-stage modal Hf age values of zircons are within analytical errors similar to two-stage Nd modal ages of whole-rocks, suggesting Paleoproterozoic crustal rocks as the major source material of the magma. A small part of zircon grains have positive �

吉林东部大蒲柴河adakites锆石U-Pb年龄、Hf同位素特征及其意义-

摘要：地球化学研究表明,大蒲柴河岩体具有典型的埃达克岩特征,来自加厚下地壳的部分熔融作用.本文采用激光等离子质谱对该岩体进行了U-Pb同位素定年,结果表明该岩体为晚侏罗世(165Ma)岩浆活动的产物.锆石的LA-MC-ICPMS Hf同位素研究结果显示,ε_(Hf)(165Ma)范围为-5.02～5.43,二阶段Hf模式年龄(t_(DM2))范围为965～1622Ma,暗示原始母岩浆为两种不同源区岩浆的混合.另外,Hf同位素研究表明,研究区在中-新元古代时(965～1304Ma)曾经历了一次重要的地壳增生事件. Abstract： Based on geochemical evidence, the quartz diorites from Dapuchai, eastern Jilin Province, belong to typical adakites derived from partial melting of thickened lower crust. Zircon U-Pb dating by LA-ICPMS technique indicates that the studied plutons were emplaced during Late Jurassic with an age of 164.9 ± 0.8Ma. Zircon Hf analyses conducted by LA-MC-ICPMS show that these adakites have variational ε_(Hf) (165Ma)values from -5.02 to 5.43, and Hf model ages from 965Ma to 1622Ma, indicating that the primary magma of the adakites originated from mixing of two different magma, one from partial melting of pre-existing crustal source that was separated from a depleted mantle source during the Middle Proterozoic; While the other magma from asthenospheric mantle through underplating during 985 ～ 1304Ma, indicative of an important crustal growth beneath the studied area.

内蒙古中部四子王旗大庙岩体时代及成因-

摘要：华北北缘的内蒙古中部地区出露大量晚古生代-早中生代花岗岩类,在空间上构成一条巨大的东西向花岗岩带.四子王旗大庙岩体作为一个典型的代表,以花岗闪长岩为主,其内部普遍发育暗色微粒包体(MMEs),是认识花岗岩岩石成因和演化的关键.本文对包体及寄主岩进行了同位素测年、岩相学、矿物化学、全岩主量元素和微量元素分析.寄主岩石中的锆石LA-ICPMS U-Pb年龄平均为265±7Ma(2σ),包体中单颗粒黑云母Rb-Sr年龄为253±5Ma(MSWD=0.85),属晚二叠世-早三叠世岩浆活动的产物.包体具塑性外形及岩浆结构,存在多种不平衡矿物组合;MME中的斜长石An组分及黑云母斑晶中MgO成分呈多期震荡,同时总体上均显示出幔部高于核、边部的特征,暗示斑晶可能为围岩捕虏晶,这种相似的成分变化指示包体与寄主岩相互作用引起的结晶环境改变,标志着岩浆成分的变化,是岩浆混合的标志之一;主量和微量数据进一步证明岩体的岩浆混合成因.Rb/Sr-K/Rb变化关系反映包体非结晶分异或黑云母堆晶的产物,而Ce/Pb-Ce、Ba-δEu和P_2O_5-δEu图及其他微量元素比值图等均表明花岗闪长岩体发生了岩浆混合作用,这也得到岩浆物理化学条件的支持.岩浆底侵和岩浆混合作用是该区岩体形成的主要机制和方式.岩石地球化学特征表明该岩体不同于加厚地壳和俯冲洋壳熔融的TTG和埃达克质岩石,而黑云母矿物化学和岩石地球化学显示其构造背景很可能为同碰撞环境. Abstract： A huge volume of Late Paleozoic to Early Mesozoic granitoids is located in the middle part of the Inner Mongolia, which constitutes a giant granitic belt trending EW. As a representative of those intrusions, the Damiao granitoid occurs in the northern portion of the Siziwangqi area, mainly composed of mid-coarse-grained granodiorite with abundant maric microgranular enclaves (MMEs) occurring. The MMEs can provide important clues

新疆哈尔里克山二叠纪碱性花岗岩-石英正长岩组合的成因及其构造意义-

东准噶尔卡拉麦里地区黄羊山花岗岩和包体LA-ICP-MS锆石U-Pb测年及地质意义-

摘要：高精度LA-ICP-MS锆石U-Pb测年结果表明,黄羊山岩浆混合花岗岩加权平均~(206)Pb/~(238)U年龄为311±12Ma,首次获得闪长质微细粒包体加权平均~(206)Pb/~(238)U年龄为300±6Ma,在误差范围内完全一致,均属于晚石炭世,前者代表黄羊山岩浆混合花岗岩成岩年龄,后者代表暗色闪长质微粒包体的形成年龄,表明两者是同时代形成的,属于300Ma前后准噶尔周边地区后碰撞岩浆活动的产物.岩石地球化学研究表明,寄主岩石具有高硅、低铝、贫钙镁、富碱和高分异的特征,寄主岩石、包体和辉绿岩脉成分均落在了混合趋势线上,寄主岩富集Rb和Th等大离子亲石元素及Zr、Hf等高场强元素,亏损Ba、Sr、Ta和Ti等元素,δEu值(为0.01)极低,具有低的~(87)Sr/~(86)Sr初始比值和高正的ε_(Nd)(t)值.黄羊山碱性花岗岩是在后碰撞拉张的构造背景下,幔源岩浆发生底垫作用,由于幔源岩浆底垫作用,下地壳温度升高而熔融形成酸性壳源岩浆,部分幔源岩浆沿着地壳中的深断裂带上涌,发生不同程度壳幔混合形成的,其中闪长质微细粒包体就是基性的幔源岩浆和酸性的壳源岩浆不同程度的混合的记录者,研究区的辉绿岩脉是幔源岩浆直接分异演化的产物. Abstract： High-precision LA-ICP-MS zircon U-Pb dating has revealed that the Huangyangshan pluton in eastern Junggar, northern Xinjiang,was formed at 311 ± 12Ma, which represents the age of lithogenesis of the Huangyangshan magma mixing pluton, and that microgranular enclaves in the alkaline granite were formed at 300 ± 6Ma. It' s the first time obtain the microgranular enclaves age in Huangyangshan pluton, which represents the age of the enclaves formed, both ages are very consistent within errors, the time belongs to Late Carboniferous, implying the host rock and its enclaves were formed at the same time, that is the product of post-collisional magma activity around the Junggar area in 300Ma approximately. Petrochemistry and

雷琼地区晚新生代玄武岩地球化学:EM2成分来源及大陆岩石圈地幔的贡献-

摘要：对雷琼地区21个晚新生代玄武岩样品的主量、微量元素和Sr、Nd、Pb同位素分别用湿化学法、ICP-MS和MC-ICPMS进行了测定.这些玄武岩主要为石英拉斑玄武岩,其次为橄榄拉斑玄武岩和碱性玄武岩.大多数样品的微量元素和同位素成分与洋岛玄武岩(OIBs)相似,而且随着SiO_2不饱和度增加,不相容元素含量也增加.除R4-1可能受到地壳混染外,其他样品相对均一的Nd同位素(ε_(Nd)=2.5-6.0)以及变化明显但范围有限的Sr同位素(0.703106～0.704481),可能继承了地幔源区的特征.~(87)Sr/~(86)Sr与~(206)Pb/~(204)Pb的正相关和~(143)Nd/~(144)Nd与~(206)Pb/~(204)Pb的负相关特征暗示DM(软流圈地幔)与EM2(岩石圈地幔)的混合.地幔捕虏体的同位素特征暗示EM2成分不可能存在于尖晶石橄榄岩地幔,而La/Yb和Sm/Yb系统表明岩浆由石榴石橄榄岩部分熔融产生,这意味着EM2成分可能存在于石榴石橄榄岩地幔.雷琼地区玄武岩的地球化学变化可以用软流圈地幔为主的熔体加入不同比例石榴石橄榄岩地幔不同程度熔融产生的熔体来解释:碱性玄武岩和橄榄拉斑玄武岩是软流圈熔体与石榴石橄榄岩地幔较低程度(7%～9%)熔融体混合,而石英拉斑玄武岩是软流圈熔体与石榴石橄榄岩地幔较高程度(10%～20%)熔融体的混合. Abstract： The major-, trace-element and Sr-Nd-Pb isotopic ratios of 21 Late-Cenozoic basalts from Leiqiong area were determined by wet chemical method, ICP-MS and MC-IPCMS, respetively. Normative mineral calculation suggested that Leiqiong basalts were dominated by quartz tholeiites with subsidiary olivine tholeiites and alkaline basalts. The trace elements and isotopic composition of these basalts resembled OIBs. In addition, the incompatible elements abundance increased with increasing SiO_2-undersaturation. The chemical and isotopic compositions of most basalts might be inherited from their mantle source except that sample R4-1 showed characteristics of cr

云南潞西三台山超镁铁岩体Os-Nd-Pb-Sr同位素特征及地质意义-

摘要：滇西地区特提斯造山带具有多块体拼合的构造特点,是东特提斯造山带的重要组成部分之一,其大地构造演化对理解全球特提斯造山带具有重要的地质意义.在腾冲和保山地块之间的龙陵-瑞丽断裂带中出露超镁铁质岩石,曾被解释为两个陆块缝合的证据.本文采用高灵敏度高精度超低本底Re-Os、Sm-Nd、Pb和Rb-Sr同位素分析技术,对采自该断裂带潞西三台山的超镁铁岩样品进行了Os-Nd-Pb-Sr同位素测定.分析结果表明,这些超镁铁岩石具有强烈富集特征.分析的5个岩石样品具有高的初始~(87)Sr/~(86)Sr值(0.71074～0.71444)、低的初始ε_(Nd)值(-6.2～-10.6)、低初始γ_(Os)值(-4.8～-8.8)和较高的初始铅同位素比值,其Os同位素模式年龄值(t_(RD))为0.97～1.71Ga.Nd-Os同位素组成特征表明,三台山超镁铁岩具有古老的富集大陆岩石圈地幔岩石的特征,不能作为腾冲和保山地块的缝合证据. Abstract： The western Yunnan Tethyan terrain that is formed by the amalgamation of multiple continental blocks represents an important part of the eastern Tethyan tectonic belt. Its tectonic evolution bears essential significances for understanding the formation of the global Tethyan orogenic belt. Along the Longling-Ruili fault zone between the Tengchong and Baoshan blocks, many small outcrops of ultramafic rocks are exposed, which have ever been interpreted as evidence for the suturing of these two blocks. Os-Nd-Pb-Sr isotopic compositions of ultramafic rocks sampled from Santaishan massif were analyzed by using low procedural blank and high precision analytical techniques in this study. Analytical results show that these ultrmafic rocks exhibit isotopic characteristics of strong enrichment. Five analyzed samples of ultramafic rock yield high initial ~(87)Sr/~(86)Sr values (0.71074 ～0.71444), low initial ε_(Nd) values (-6.2 ～ -10.6), low initial γ_(Os) values (-4.8 ～ -8.8) and relative high initial Pb isotopic ratios. Os isotopic mod

滇西吉义独蛇绿混杂岩的岩石地球化学特征、成因和构造环境探讨-

摘要：滇西吉义独蛇绿混杂岩位于金沙江缝合带的南端,岩石组合出露较齐全,包括堆晶橄榄岩、堆晶辉石岩、堆晶辉长岩以及玄武岩等,它们呈构造岩片的形式产出并与外来岩块组成蛇绿混杂岩.堆晶橄榄岩和辉石岩具低Al_2O_3,低TiO_2,而高Mg~#值(Mg~#=0.88～0.92),富集Cr和Ni,稀土总量偏低(∑REE=14.82×10~(-6)～27.75×10~(-6)),倒"U"型的稀土元素分布特征.堆晶辉长岩和玄武岩的Mg~#值较低,分别为0.70～0.79和0.51～0.66,具拉斑系列的演化趋势.玄武岩可以细分为2组:第一组玄武岩以平坦型稀土配分模式,低Mg~#(Mg~#=0.44～0.46),低稀土总量(∑REE=52.29×10~(-6)～60.26×10~(-6))为特征;第二组玄武岩则为LREE弱富集型的稀土配分模式,其Mg~#较高(Mg~#=0.54～0.68),稀土总量也较高(∑REE=62.13×10~(-6)～101.87×10~(-6)).在原始地幔标准化的微量元素配分图解中,两组玄武岩均相对富集大离子亲石元素而亏损Nb、Ta和Ti,与岛弧岩浆岩类似,明显不同于N-MORB.岩石的Sr-Nd同位素组成较为均一和稳定,堆晶橄榄岩和辉石岩的(~(87)Sr/~(86)Sr)_i=0.7051～0.7056,5_(Nd)(t)=2.8～4.1,玄武岩的(~(87)Sr/~(86)Sr)_i=0.7050～0.7056,ε_(Nd)(t)=5.1～5.8,且显示出原始地幔的同位素组成特征,暗示这些岩石为同源岩浆分异演化而成的岩浆产物.岩浆演化的主要方式为分离结晶作用,受地壳混染不明显.岩浆结晶形成岩石的顺序为:堆晶橄榄岩→堆晶辉石岩→堆晶辉长岩→玄武岩2组→玄武岩1组.岩石地球化学特征表明,吉义独蛇绿岩的形成与俯冲作用有关,且形成于金沙江洋内俯冲的消减环境. Abstract： The Jiyidu ophiolitic melange in the southern end of the Jinshajiang suture zone, west Yunnan Province, consist mainly of basic and ultrabasic rocks and limestones showing characteristics of a typical variably disrupted ophiolitic suite. The peridotites and pyroxenites are uhrabasic cumulus rocks, the basic unit includes cumulus gabbros,

南秦岭大堡组奥陶纪洋岛玄武岩的识别及其构造意义:来自地球化学和年代学证据-

摘要：秦岭造山带以商-丹构造带为界分为北秦岭和南秦岭构造带.大堡组位于南秦岭构造带内,由灰色-深灰色的泥岩、粉砂岩和炭硅板岩,以及夹含炭硅质岩、灰岩和基性火山岩块体组成.在大堡组中出露的能干上和蚂蝗峡基性岩块夹于黑色的泥岩之中,岩石地球化学分析结果表明,SiO_2含量为41.53%～53.59%,富TiO_2为2.14%～3.58%,REE的总量为∑REE=282.3×10~(-6),轻稀土元素较重稀土元素富集[(La/Yb)_N=8.34],略显Eu正异常(Eu~*=1.13～1.25),具有较高的Ti/Y(300～622)和Zr/Y(3.8～7.4)比值.大离子亲石元素Rb、Ba和K相对富集,无明显的Nb和Ta异常,其Nb和Ta值为N-MORB标准值的10～20倍,为典型洋岛玄武岩(OIB)地球化学特征.锆石SHRIMP Ⅱ U-Pb测年获得能干上和蚂蝗峡基性岩块体分别形成于446Ma和455Ma.这些资料进一步表明,奥陶纪时期南秦岭存在着古洋盆. Abstract： The Qinling orogen is divided into northern and southern Qinling tectonic belts by Shangxian-Danfeng tectonic melange. The Dabao Formation is located in the southern Qinling orogen and is composed of grey and dark grey mudstone, siltstone, silicic slate matrix and chert, limeatone and basalt blocks. The Nengganshang and Mahuangxia basalt blocks are contained within black mudstone matrix in Dabao Formation. Based on geochemical analysis, the Nengganshang and Mahuangxia basalt blocks have similar geochemical characteristics to those of OIB, with high SiO_2 (41.53% ～ 53.59%), high TiO_2 (2.14% ～3.58%), Fe_2O_3~T (10.23% ～ 15.64%), high REE (282.3 × 10~(-6)) contents, high Ti/Y (300 ～ 622) , Zr/Y (3.8 ～ 7.4), and show enrichment light REE[ (La/Yb)_N = 8.34], weak Eu positive anomaly (Eu~* =1.13 ～1.25), without abnormity in Nb and Ta, and enrichment in Rb, Ba and K. The zircon SHRIMPⅡ U-Pb dating results yielded ages of 446Ma and 455Ma in Nengganshang and Mahuangxia basalt blocks. The data suggests the existence of an ocean basin in south Qinling during Ordovician.

地幔包体金云母~(40)Ar/~(39)Ar年龄对玄武岩浆喷发结束时间的约束-

摘要：山东临朐-昌乐地区新生代岩浆活动强烈,以形成含大量地幔包体的玄武岩为特征.作者在考察与研究昌乐北岩古火山口玄武岩中地幔包体的过程中,发现一些包体中发育有地幔钾交代成因的金云母细脉.鉴于金云母的封闭温度远低于玄武岩浆喷发时的温度以及金云母可以记录喷发的玄武岩浆冷却通过金云母封闭温度的时间,本文尝试通过金云母所记录的~(40)Ar/~(39)Ar年龄来推断玄武岩浆喷溢的结束时间.该火山口玄武岩不同部位的三个地幔岩包体其金云母的~(40)Ar/~(39)Ar坪年龄分别为18.42±0.21Ma、18.65±0.27Ma和18.39±0.36Ma,年龄结果具有很好的一致性,充分说明了该定年手段的有效性.因此可以确定该火山口玄武岩浆喷溢活动约在18.5Ma前结束.由此推测山旺盆地中不整合发育在源于该火山口喷溢的玄武岩之上的化石群的形成时代下限约为18.5Ma.用玄武岩地幔包体金云母的~(40)Ar/~(39)Ar年龄来确定玄武岩年龄是玄武岩定年一个有效的新方法. Abstract： Cenozoic basalts in the Linqu-Changle area, Shandong Province, are characterized by abundant mantle-derived xenoliths. Recently, we discovered that some xenoliths in the Beiyan paleovolcanic crater contain some fine phlogopite veins related to mantle K-metasomatism. Since the closure temperature of phlogopite is much lower than the eruptive temperature of basaltic magma and the phlogopite has potential to record the time when hot magma cool down through the closure temperature of phlogopite, here we try to use the ~(40)Ar/~(39)Ar age of phlogopites to determine the ending time of eruption of basaltic magmas and age of basalt in the Beiyan paleovolcanic crater. Three phlogopite samples from three mantle-derived xenoliths from different positions in the Beiyan paleovocanic crater yielded identical ~(40)Ar/~(39)Ar plateau ages of 18.42±0.21Ma, 18.65±0.27Ma and 18.03±0.63Ma respectively. It is concluded that the basaltic volcanic act

青藏高原北部新生代走构油茶错、纳丁错火山岩年代学、地球化学特征及其构造意义-

摘要：本文对分布于藏北南羌塘地区的走构油茶错和纳丁错新生代火山岩进行了岩石学、同位素年代学和地球化学研究.两个地区火山岩主要由粗面玄武岩、橄榄粗安岩、安粗岩及粗面岩组成,具有从碱性系列火山岩到高钾钙碱性火山岩连续演化的特征.锆石U-Pb定年表明两个地区火山岩形成时代分别为34.64±0.55Ma和35.03±0.54Ma,另外在走构油茶错安粗岩和粗面岩中发现了大量的捕获锆石.地球化学分析显示,岩石ε_(Hf)(t)均为正值,但随SiO_2含量的增高,ε_(Hf)(t)有减小的趋势.稀土元素配分曲线上轻重稀土分馏明显,无或轻微Eu负异常,尤其是重稀土出现分馏,大多数样品(Sm/Yb)_N值介于6.30～8.25之间,表明原生岩浆起源于含有石榴石的弱亏损型软流圈地幔,中酸性岩浆所具有的类似埃达克岩的地球化学特征是原生幔源岩浆经AFC作用形成的.始新世末期南羌塘地区的火山活动可能与向北俯冲的拉萨地块的岩石圈地幔断离造成的软流圈上涌有关. Abstract： This paper reported petrology, geochronology and geochemistry of the Cenozoic volcanics from Zougouyouchacuo and Nadingcuo in South Qiangtang area, northern Tibetan Plateau. The volcanic rock in the study area is mainly composed of trachybasalt, mugearite, latite and trachyte. The volcanics show evolutionary trend from alkaline series to high-K calk-alkaline series. Zircon U-Pb dating indicates the volcanic rocks in Zongouyouchacuo and Nadingcuo area were formed in 34.64 ± 0.55Ms and 35.03 ± 0.54Ma respectively, besides there are lots of captured zircons in Zougouyouchacuo latite and trachyte. All of the samples have positive ε_(Hf)(t) values, but ε_(Hf)(t) decreases with the increase of SiO_2. The fractionation between LREE and HREE is obvious, without or having minor negative Eu anomalies. The fractionation between HREE is also notable, with (Sm/Yb)_N = 6.30 ～ 8.25, which indicates the primary magma originated from weakly depleted

信阳周庄变辉长岩LA-ICPMS U-Pb定年与华北南缘复杂演化过程-

摘要：河南信阳周庄变基性侵入岩体出露于华北克拉通南缘,主要由斜长石+角闪石(+绿帘石)组成,可见残余辉长结构,属经历了绿帘角闪岩相-低角闪岩相变质的变辉长岩.对变辉长岩的两个样品中的锆石进行了LA-ICPMS U-Pb同位素测年分析.这两个样品都给出了859Ma的谐和上交点年龄,但分别给出了356±82Ma和234±36Ma的谐和下交点年龄.其中一个样品还给出了另外两组谐和的年龄,它们的~(206)Pb/~(238)U表面年龄分别是616±10Ma和442±6.5Ma.我们解释共同的谐和上交点年龄(859Ma)代表着岩体的侵位时代,是Rodinia超大陆裂解事件在华北克拉通南缘的早期记录(如基性岩浆侵入作用);其他四组年龄是岩体后期所经历改造事件的年龄记录,包括新元古代晚期的再次裂解(如变质重结晶作用)和古生代、早中生代时期扬子克拉通向北的俯冲-碰撞对华北南缘的强烈改造过程. Abstract： Zhouzhuang meta-basic pluton in Xinyang, Henan Province, locates at the southern margin of the North China Craton. It is mainly composed of plagioclase + amphibole (+ epidote). The relict-gabbro texture can be found in some samples, suggesting that the rocks belong to meta-gabbro experienced epidote-amphibolite facies-low-amphibolite facies metamorphism. Zircons of two samples were analyzed, using LA-ICPMS for U-Pb ages. Both samples give concordant upper intercept age of 859Ma, but concordant lower intercept ages of them are 356 ±82Ma and 234±36Ma, respectively. One sample also gives another two groups of the concordant ages with the ~(206)Pb/~(238)U ages of 616±10Ma and 442±6.5Ma. We interpret the upper intercept age of 859Ma as the intruding age of the basaltic magmatism, corresponding to the breakup of the Rodinia Supercontinent, which recorded at the southern margin of the North China Craton; the others record that the pluton underwent subsequent metamorphism and modifications, including the rifting event at the southern margin of the North C

辽西北票蓝旗组火山岩锆石U-Pb年龄和Hf同位素组成-

摘要：辽西北票常河营子地区有中生代蓝旗组火山岩分布,其中上部安山质角砾熔岩的锆石LA-ICPMS U-Pb年龄分析结果表明,其结晶年龄为159.4±3.4Ma,属晚侏罗世.锆石~(176)Hf/~(177)Hf比值介于0.282098～0.282789之间,ε_(Hf)(t)值为-20.4～+4.1,主体分布在华北克拉通地壳演化线之上,位于古元古代地壳演化范围内,所给出的亏损地幔年龄(t_(DM))和平均地壳模式年龄(t_(crust))分别为0.7～1.6Ga和0.9～2.5Ga.结合已发表蓝旗组中酸性火山岩的岩石地球化学及Sr-Nd同位素组成特征,我们认为安山质火山岩源于古老(如晚太古代)下地壳玄武质岩石的部分熔融,其形成过程可能与中生代幔源岩浆底侵作用有关. Abstract： Large-scale volcanic rocks of the Lanqi Formation are developed in the Changheyingzi area, western Liaoning Province. LA-ICPMS zircon U-Pb dating gives the Late Jurassic eruption age for andesitic breccia lava of the Lanqi Formation as 159.4 ± 3.4 Ma. In-situ zircon Hf analyses show that Lanqi Formation have ~(176)Hf/~(177)Hf values of 0.282098 to 0.282789, ε_(Hf)(t) values of -20.4 to + 4.1, t_(DM) (depleted mantle model age) of 0.7 ～ 1.6Ga and t_(crust)(average crustal model age) of 0.9 ～2.5Ga, respectively. Combining the published geochemical data of the volcanic rocks, especially their Sr-Nd isotopic compositions, we interpret the andesitic volcanic rocks as products mainly derived from the partial melting of Neoarchean basaltic rocks in the lower crust due to the basaltic magmas underplating in Mesozoic time.

奥陶纪-志留纪边界附近火山活动记录:来华南周缘钾质斑脱岩的信息-

摘要：扬子地台内奥陶纪顶部的五峰组到志留纪底部的龙马溪组间存在着多个粘土岩层.前人研究结果认为这些粘土岩层为钾质斑脱岩,是火山喷发的凝灰质物质在海相环境沉积、蚀变的产物.这些斑脱岩广泛分布于扬子地台周缘,对理解奥陶纪-志留纪时华南所处的大地构造位置和相应的构造事件具有重要的意义.本文对采自扬子地台内湖北宜昌地区和贵州桐梓地区奥陶纪-志留纪界线剖面的斑脱岩层进行了矿物学及地球化学工作,旨在判定其形成的构造环境.矿物学研究表明上述岩石除了含有粘土矿物外,还含有石英、长石、黑云母、磷灰石、锆石等中酸性岩浆岩中的常见矿物,属典型的钾质斑脱岩.本文利用在风化过程中不活动元素对斑脱岩的原岩进行了恢复,结果也表明其原岩为中酸性火山岩,包括安山岩-英安岩-及流纹岩等.微量元素特征显示多数样品具有典型的岛弧火山岩的特征,很可能与北面早古生代秦岭洋的闭合过程中的板块俯冲有关,也可能是早古生代在华南板块东南缘外侧存在的一古老洋壳向华南板块的俯冲.有一个样品(YC0711)没有Nb的负异常,但是具有明显的Ti负异常,在Th/Yb-Nb/Yb判别图上落在岛弧区附近,其原岩可能是富铌玄武岩之类的特殊岛弧岩石.火山活动的峰期为晚奥陶世赫南特阶时代,与地质历史上第二大的生物大灭绝事件同时.前人认为该生物灭绝事件与冈瓦纳冰川有关.考虑到华南以及欧洲、北美等地均出现大规模晚奥陶世-早侏罗纪钾质斑脱岩,奥陶纪-志留纪边界的火山事件是具有全球规模的,所喷发的岩石多是富含挥发份的中酸性岩,对大气圈和生物圈具有十分重要的影响,本文认为火山活动很可能是造成晚奥陶世的生物大灭绝事件和冈瓦纳冰川的主要诱导因素. Abstract： There are several clay beds recognized from the Wufeng Formation, the top of the

扬子地块北缘西乡群孙家河组火山岩形成时代及元素地球化学研究-

摘要：西乡群孙家河组为一套低绿片岩相浅变质火山-沉积岩系,主要由基性-中基性-酸性火山岩和凝灰岩、沉凝灰岩、泥岩、硅质岩组成,火山岩岩石类型包括玄武岩、安山岩、英安岩和流纹岩.LA-ICPMS锆石U-Pb定年揭示流纹岩形成时代为832.9±4.9Ma,辉石玄武岩的形成时代为845.0±17Ma,两者在误差范围内一致,属新元古代同期岩浆作用产物.元素地球化学研究表明,孙家河组玄武岩属拉斑玄武岩系列,具有受地壳混染的板内玄武岩的地球化学特点.玄武岩-安山岩-英安岩主量元素成分投点呈规律性变化、REE球粒陨石标准化及微量元素原始地幔标准化分配型式具有一致性并相互重叠,不相容元素Th和相容元素Cr相关模拟图中沿分离结晶线分布,证明玄武岩-安山岩-英安岩为同一基性岩浆分离结晶的产物.REE和微量元素分配型式以及微量元素比值对的显著差异,暗示流纹岩与玄武岩-安山岩-英安岩来源于不同源区.Sr-Nd同位素研究表明,玄武岩-安山岩-英安岩样品的ε_(Nd)(t)值均大于0以及在ε_(Nd)(t)-(~(87)Sr/~(86)Sr)_t图解中位于OIB成分区,表明其源区应为与洋岛玄武岩类似的地幔源区;流纹岩样品具有可与基性熔岩相比拟的ε_(Nd)(t)值,暗示流纹岩最有可能是初生玄武质地壳部分熔融而成.本文所研究的原划孙家河组火山岩系列的形成时代、构造环境的确定以及扬子陆块乃至世界上同一时间内普遍发育大陆裂谷岩浆岩组合的地质事实,说明原划孙家河组以及西乡群中的确存在新元古代的组成部分,它们应是新元古代大陆裂谷的产物,它和扬子地块820M8后造山裂解环境花岗岩均是新元古代晚期Rodinia超大陆裂解作用的岩浆响应. Abstract： The Sunjiahe Formation is a suit of low-metamorphosed volcano-sedimentary association, and is composed of basic, intermediate-basic and acid volcanic rocks with interbedding tuff, sediment-tuff, mudston