共查询到20条相似文献，搜索用时 140 毫秒
1.
西藏那曲县北聂荣微地块聂荣岩群中斜长角闪岩——Rodinia超大陆裂解的地质纪录 总被引：7，自引：0，他引：7
西藏那曲县北聂荣微地块聂荣岩群中斜长角闪岩原岩恢复为正斜长角闪岩,地球化学特征显示岩石属于拉斑系列基性火山岩,具有轻稀土元素富集、重稀土元素亏损的右倾型稀土元素配分模式。岩石富集大离子亲石元素Rb、Ba及高场强元素Nb、Ta,Sr、Th和U呈现明显的负异常,在构造环境判别图解中样品均投到板内玄武岩区,具有与裂谷火山岩相似的地球化学特征。通过高精度的LA-ICP-MS(激光剥蚀等离子体质谱仪)锆石微区原位U-Pb同位素测年,西藏那曲县北聂荣微地块聂荣岩群片麻状斜长角闪岩中获得863±10 Ma的谐和年龄,为原岩(基性火山岩)的形成时代,说明聂荣岩群形成于新元古代早期。该年龄相当于Rodinia超大陆裂解的地质记录。此外,还获得了2 539~1 006 Ma之间的捕获锆石年龄信息。 相似文献
2.
兴华渡口岩群作为额尔古纳地块的基底,其变质年龄、原岩类型及大地构造背景一直是地质学家关注的热点。以大兴安岭北段绿林林场一带兴华渡口岩群作为研究对象,利用锆石U-Pb同位素测年限定了原岩的变质时代,结合岩相学与地球化学综合分析方法开展原岩恢复,并进一步讨论了其形成的大地构造背景。研究认为兴华渡口岩群主要由斜长角闪岩类、浅粒岩类、变粒岩类和石英岩类组成;斜长角闪岩类原岩为基性火山岩,浅粒岩类原岩为英安质凝灰岩,石英岩和变粒岩原岩为泥质粉砂岩;斜长角闪岩类亏损非活动性微量元素Ta、Nd、P,大地构造环境属岛弧环境;浅粒岩类主要亏损Ta、Nd、P、Sr、Ti等元素,形成于大陆边缘造山带环境。绿林林场一带兴华渡口岩群的变质年龄下限为774.1±3.8 Ma。 相似文献
3.
拉陵灶火中游基性变质岩体原岩侵位于古元古界金水口岩群白沙河岩组片麻岩之中。文章对基性变质岩体开展了岩相学、年代学和岩石地球化学研究,探讨了其原岩及源区性质、成岩构造环境、年龄及地质意义。结果表明,基性变质岩为斜长角闪岩、变质辉绿岩和角闪岩,原岩应属于亚碱性系列岩石,既有拉斑系列,又有钙碱性系列和钾玄质系列。岩石中SiO2含量为44.04%~54.39%,全碱（Na2O+K2O）含量为1.97%~6.53%、且Na2O>K2O,MgO含量为5.01%~9.58%,TFe2O3含量为7.71%~13.46%,TiO2含量为0.56%~1.49%;ΣREE平均为83.60×10-6,δEu为0.89~1.55,平均为1.14,呈轻微正异常;稀土元素球粒陨石标准化配分模式图上呈稍右倾的较平滑曲线,具有轻、重稀土轻微分异的轻稀土略富集特征;岩石明显富集大离子亲石元素Cs、Rb、Ba、K、Sr、U、Pb,显著亏损高场强元素Nb、Ta、Zr,略微亏损P和Ti。采用SIMS锆石U-Pb定年,结合岩石地球化学和区域地质背景,认为拉陵灶火中游地区斜长角闪岩记录了新元古代早期（928±25 Ma）、早寒武世末期（514±11 Ma）、中晚奥陶世（451±11 Ma）和早中泥盆世时期（392±12 Ma）的岩浆—变质事件,其中928±25 Ma和514±11 Ma是斜长角闪岩捕获的锆石年龄,451±11 Ma 是斜长角闪岩的原岩结晶年龄,392±12 Ma是斜长角闪岩的变质年龄。拉陵灶火中游基性变质岩体原岩是俯冲板片脱水交代的岩石圈地幔部分熔融的产物,应形成于岛弧环境。 相似文献
4.
为了解赣中周潭群的构造属性和华夏陆块的演化历史,本文对崇仁地区的斜长角闪岩开展了锆石U-Pb年代学和地球化学研究。结果表明,崇仁地区斜长角闪岩形成年龄为(870±9) Ma,其SiO_2含量为51. 22%～53. 11%,MgO为6. 16%～6. 74%,TiO_2为1. 23%～1. 40%,原岩为拉斑玄武岩。崇仁地区斜长角闪岩LaN/YbN值为1. 85～2. 12,GdN/YbN值为1. 10～1. 17,与E-MORB相比富集大离子亲石元素。样品亏损高场强元素,具有明显的Nb-Ta异常、Nb/La=0. 50～0. 72。样品的εNd(t)值为5. 1～6. 0,其源区为受俯冲组分改造的地幔楔,其构造背景为弧后盆地。结合前人在华夏陆块的工作,推测崇仁相山新元古代～870 Ma斜长角闪岩与北侧的弋阳周潭群火山岩指示了华夏内部新元古代弧后盆地的存在。 相似文献
5.
文章报道了浙江"陈蔡增生杂岩"中新发现一类特殊的变质基性火山岩组合,主要由斜长角闪岩和角闪岩组成,岩石具有低Ti高Mg的地球化学特征,原岩为拉斑玄武岩和钙碱性玄武岩。岩石稀土总量较低,ΣREE平均为25.46×10~(-6),轻重稀土比值LREE/HREE及(La/Yb)_N比值较小,平均分别为1.87和1.30,δEu平均为0.97,稀土配分与N-MORB及T-MORB类似,而微量元素显示为富集相容元素Cr、Ni及大离子亲石元素(LILE)K、Rb、Ba、U,亏损高场强元素(HFSE)Nb、Zr、P、Ti。上述地球化学特征与玻安质岩石十分相似,微量元素比值及图解判别均指示该套变基性火山岩形成于大洋岛弧(洋内弧)环境。该洋内弧型变基性火山岩的发现表明原定陈蔡群极有可能为新元古代中期至早古生代含有古大洋地壳残片的俯冲增生杂岩,而不是华夏古陆块的基底。 相似文献
6.
扎兰屯地区位于贺根山-黑河构造带中段，发育叠加韧性变形的晚古生代岩浆岩，可较好地记录这一时期的构造演化历史，但其研究程度较低.在野外调查基础上，对扎兰屯头道沟花岗质糜棱岩中的斜长角闪岩构造透镜体进行年代学和地球化学研究，探讨其成岩、变质及构造意义.头道沟斜长角闪岩原岩为玄武安山岩，锆石LAICP-MS U-Pb年龄为373.0±2.6 Ma，相当于大民山组火山岩.该岩石属钠质岩石，富集大离子亲石元素和轻稀土元素，亏损高场强元素，锆石原位εHf（t）为+5.39~+10.06，类似兴安岛弧的Hf同位素特征.上述特征暗示其原岩可能起源于蚀变洋壳流体交代亏损地幔演化而来的年轻下地壳，形成于板块消减带之上的前弧盆地.晚泥盆世在额尔古纳-兴安地块东南缘发育弧后、弧间和弧前盆地.斜长角闪岩变质年龄为~241.5±9.6 Ma，该变质可能与天山-兴蒙造山带演化晚期的伸展作用有关. 相似文献
7.
对辽东桓仁地区辽河群高家峪组中出露的斜长角闪岩进行岩石学、地球化学及年代学研究,显示高家峪组中的斜长角闪岩原岩为基性玄武岩,可划分为低Ti E MORB及高Ti OIB两种类型:低Ti型样品原岩属拉斑玄武岩系列,轻微亏损Nb、Ta、Zr,明显亏损P,弱轻稀土富集、重稀土亏损,具有E-MORB地球化学特征;高Ti样品原岩属碱性玄武岩系列,富集Rb、Th、U等大离子亲石元素,轻稀土富集、重稀土亏损,具有OIB地球化学特征.两类斜长角闪岩具有较低的MgO、Cr、Ni含量及Mg#值,说明它们原岩不是原始岩浆,而是通过不同矿物相分离结晶作用形成.锆石U-Pb测年表明低Ti型和高Ti型斜长角闪岩成岩年龄分别为2158±15 Ma、2173±12 Ma,变质年龄分别为1870±6 Ma、1861±7 Ma.区域地质特征及岩石成因研究共同指示两类斜长角闪岩形成于弧后盆地环境,辽吉地区在古元古代早期可能处于活动大陆边缘弧后盆地构造环境,辽吉造山带的形成与弧-陆碰撞有关. 相似文献
8.
扬子西缘江浪穹窿核部里伍岩群的形成时代及构造背景 总被引：1，自引：0，他引：1
江浪穹窿位于扬子陆块西缘,核部地层里伍岩群为一套变质的火山-沉积岩系。为精确厘定里伍岩群的形成时代并探讨其成岩构造背景,本文进行了LA-ICP-MS锆石U-Pb年代学以及岩石地球化学研究。定年结果表明变沉积岩中碎屑锆石年龄介于2521~262 Ma,其中最年轻一组岩浆成因锆石的~(206)Pb/~(238)U加权平均年龄为552.8±5.7 Ma(MSWD=2.1,n=6)。变沉积岩SiO_2含量变化很大(53.48%~96.08%),显示明显的Eu负异常(Eu/Eu*=0.50~0.67),相对富集大离子亲石元素(Rb、Ba和U等)、亏损高场强元素(Nb、Ta、Zr、Hf和Ti等),其稀土、微量配分模式与大陆上地壳完全一致。变基性火山岩具有很低的SiO_2含量(39.92%~48.27%),其稀土、微量配分模式平坦,类似于E-MORB。结合变基性火山岩的锆石U-Pb定年结果(542±9.0 Ma),本文指出里伍岩群应当形成于新元古代晚期(553~542 Ma),而并非前人所认为的古元古代或中元古代。变沉积岩的物源区主要为扬子西缘新元古代地质体,与变基性火山岩均形成于Gondwana超大陆聚合之后的板片俯冲环境。此外,碎屑锆石的年龄谱反映江浪穹窿可能存在太古宙—古元古代变质基底,并且具有Rodinia超大陆的会聚-裂解事件以及加里东运动的地质年龄记录。 相似文献
9.
哀牢山-大象山变质杂岩带位于青藏高原东南缘，是西南三江地区重要的北西向造山带。杂岩带主要由各种类型的副片麻岩、片岩、石英岩、大理岩和斜长角闪岩构成，岩石发生强烈的糜棱岩化。本文在哀牢山变质杂岩带东南段元江和金平地区以及大象变质杂岩带北段老街和Pho Rang地区发现了中二叠-早三叠世的斜长角闪岩。岩石地球化学和锆石U-Pb年龄研究表明，这些斜长角闪岩可分为4组：第1组为元江斜长角闪岩，具有类似于E-MORB的稀土和微量元素配分曲线特征，锆石U-Pb定年显示其原岩形成年龄为272.5±1.7Ma；第2组为勐桥-马鞍底斜长角闪岩，相比于元江斜长角闪岩（第1组）具有更高的轻/重稀土分馏程度，其稀土和微量元素配分曲线类似于E-MORB，微量元素比值（Nb/Yb、Th/Yb等）显示具有沿MORB-OIB序列演化的趋势，勐桥和马鞍底斜长角闪岩中的Ti含量和Ti/Y比值等特征分别类似于峨眉山低Ti玄武岩和高Ti玄武岩。锆石U-Pb定年结果表明，勐桥-马鞍底斜长角闪岩形成于265.2±1.0Ma~266.2±1.0Ma和250.4±1.5Ma~248.7±1.6Ma，其中晚期岩石中含有261.2±1.5Ma~257.9±1.6Ma的继承锆石，该年龄与峨眉山玄武岩（约260Ma）近于同期。上述证据表明勐桥-马鞍底斜长角闪岩岩浆演化过程中可能混染了部分具有OIB属性的峨眉山地幔柱物质成分；第3组为大象山老街-Pho Rang斜长角闪岩，具有类似于OIB的稀土和微量元素配分曲线特征，微量元素含量和比值（TiO2=3.28%~4.31%，Nb/La=0.84~1.01，Ti/Y>500等）特征显示与峨眉山高Ti玄武岩相似的地球化学属性，表明峨眉山玄武岩在哀牢山-大象山变质杂岩带内广泛分布，该岩石成分可能为勐桥-马鞍底斜长角闪岩（第2组）的端元组分之一；第4组为大象山Pho Rang斜长角闪岩，该组岩石具有与元江斜长角闪岩（第1组）相似的E-MORB属性特征。进一步的研究表明，哀牢山-大象山变质杂岩带中具有类似于E-MORB属性的斜长角闪岩均表现出不同程度的Nb、Ta元素亏损和Rb、Ba等大离子元素富集，微量元素比值（Nb/Yb（0.72~5.29），Th/Yb（0.11~0.87），La/Nb（0.91~8.83））等特征类似于岛弧玄武岩，这些特征指示其原岩岩浆可能是俯冲环境下地幔楔岩石部分熔融的产物。结合哀牢山-大象山变质杂岩带、哀牢山-马江缝合带以及扬子地块之间的时-空关系，本文推测哀牢山-大象山变质杂岩带内的E-MORB类型岩浆岩形成于东古特提斯支洋（即哀牢山-马江洋）向东的俯冲过程，其俯冲持续时间为中二叠-早三叠世（272~248Ma）。 相似文献
10.
山东沂水杂岩中变基性岩的岩石地球化学特征及锆石SHRIMP U-Pb定年 总被引：7，自引：0，他引：7
山东沂水杂岩由新太古代岩浆杂岩和中太古代的变质杂岩组成,其后者中的变基性岩石,特别是基性麻粒岩,常与紫苏花岗岩紧密伴生,而且多呈大小不等的包体或呈层状体产出。本文主要对变基性岩进行岩石地球化学和锆石SHRIMP UPb定年研究。根据岩石学特征,可将变基性岩分为三类：含紫苏辉石斜长角闪岩、含石榴子石角闪二辉斜长麻粒岩和含尖晶石—石榴子石的角闪二辉麻粒岩。它们原岩分别为安山质玄武岩、高铁镁质玄武岩和玄武质科马提岩（？）。三类岩石稀土元素和微量元素配分有一定差别：第一类含紫苏辉石斜长角闪岩富集轻稀土和大离子亲石元素,亏损Nb、Ta、Zr、Hf等高场强元素;后二类麻粒岩相变质岩的稀土配分模式为近平坦型或轻稀土略为富集, K、Rb、Ba等元素也轻微富集,其他元素与MORB的比值接近于1。变基性岩中锆石定年结果显示有四组年龄值,其中2719Ma和2560～2607Ma分别代表早期麻粒岩相变质作用的年龄下限和上限;2509～2522Ma代表另一期角闪岩相—麻粒岩相变质作用的时代,发生在沂水岩浆杂岩侵入之后;2485Ma和2497Ma代表与流体作用有关的变质作用和新生锆石的形成年龄。 相似文献
11.
A sequence of amphibolite to granulite facies metasedimentary and mafic metaigneous rocks from the western Italian Alps has been analysed for rare earth elements (REE). In this sequence, the metasedimentary granulites have probably been affected by a melting event while the metaigneous granulites remained unaffected. Metasedimentary granulites have a less fractionated chondrite-normalized REE pattern than equivalent amphibolite facies rocks. The granulites tend to have a higher content of heavy REE and lower abundances of light REE (LREE). The leucosomes of migmatitic granulites have lower REE content than the melanocratic bands and both these rock types have variable relative abundances of Eu. The mafic granulites have LREE enriched patterns while the amphibolites are slightly depleted in LREE. The differences between the mafic granulites and amphibolites are probably of pre-metamorphic origin. 相似文献
12.
The whole-rock chemistry of eclogites, partially amphibolitized eclogites, and dyke amphibolites from the metamorphic Kechros complex in the eastern Rhodope Mountains preserves evidence of the geodynamic framework for the origin of their protoliths. Major and trace-element concentrations define two distinct protolith groups for the eclogites. The low-Fe–Ti (LFT) eclogites have low-TiO2 content (<0.67 wt%), negative high field strength element anomalies, and variable enrichments in large ion lithophile elements (LILE). The rare earth element (REE) patterns are characterized by strong light-REE (LREE) enrichment and heavy-REE (HREE) depletion. The high-Fe–Ti (HFT) eclogites have small to moderate LILE enrichment and lack Nb anomalies. The REE patterns of the HFT eclogites are characterized by LREE depletion and relatively flat MREE–HREE patterns. The rock compositions and petrographic features of the LFT eclogites resemble gabbros formed in a continental rift environment with minor to moderate contamination of a mantle-derived mafic magma by continental crust, whereas the HFT eclogites resemble mafic rocks formed in extensional oceanic environments. We interpret the HFT suite to represent a later stage in an evolution from continental rift to open ocean, following the origin of the LFT suite. Dyke amphibolite compositions, except for probable SiO2 loss associated with metamorphic dehydration reactions, appear to represent liquid compositions quenched in conduits through the lower crust. MELTS modeling shows that dyke amphibolite compositions can be related to each other by fractional crystallization under strongly oxidizing conditions at ~0.5 GPa pressure, and all can be derived from a low-degree melt of modified fertile peridotite from around 1.7 GPa. Cumulates crystallized from the parental liquids of the amphibolites under oxidizing conditions may have yielded the protoliths of the HFT suite. 相似文献
13.
《International Geology Review》2012,54(1):130-156
New mineralogical and chemical data for ophiolitic rocks from the southwesternmost Liguride Units are presented in order to constrain their ocean-floor origin and subsequent emplacement in an accretionary wedge. Their complete petrochemical evolution is particularly well preserved in the southern Apennine metabasites. Metadolerites show amphibolite and greenschist facies mineral assemblages of ocean-floor metamorphism. Metabasalts display greenschist facies ocean-floor metamorphism and spilitic alteration. Veins cutting the mafic rocks show mineral assemblage of the prehnite–pumpellyite metamorphic facies. HP/LT orogenic metamorphism, reflecting underplating of the ophiolitic suite at the base of the Liguride accretionary wedge during subduction of the western Tethys oceanic lithosphere produced a mineral assemblage typical of the lawsonite–glaucophane facies. Bulk-rock chemistry suggests that the mafic protoliths had a MORB-type affinity, and were affected by ocean-floor rodingitic and/or spilitic alteration. Hydrothermal alteration-induced LREE mobility and LREE enrichment may be correlated with the ocean-floor metamorphism. 相似文献
14.
一、地质概况白乃庙铜矿区位于内蒙古自治区四子王旗白音朝克图公社。属天山—阴山纬向构造带北缘。矿区地层称白乃庙群(Zb),自下而上暂分五个岩段,其岩性如下: 第一岩段(zb~1):变粒岩、黑云斜长片麻岩、硅线石黑云片麻岩、石榴石二云片岩、斜长角闪岩等。 相似文献
15.
河北小觉地区阜平岩群斜长角闪岩及深熔产物的稀土和Nd同位素地球化学研究 总被引：5，自引：0，他引：5
工作中重点对河北平山小觉地区阜平岩群两类角闪质岩石深熔作用的地球化学进行了研究。一类为厚层状斜长角闪岩，相邻新生浅色体常量元素组成上向TTG花岗质岩石方向转化，稀土和高场强元素含量明显降低，轻重稀土分离程度增高，tDM减小，εNd(t0)增大。另一类为与黑云变粒岩－片麻岩互层的条带状、石香肠状斜长角闪岩，相邻新生浅色体与之存在不同的地球化学关系：（1）稀土总量相对增高，轻重稀土分离程度有所降低；（2）稀土总量和轻重稀土分离程度都有明显增高。后者Nd同位素组成与斜长角闪岩也存在很大区别。这些现象可用熔融母岩、形成条件等差异得到合理的解释。 相似文献
16.
锡林浩特岩群是内蒙古中东部锡林郭勒微地块内原锡林郭勒杂岩的重要组成部分,由一套片麻岩夹层状斜长角闪岩、磁铁石英岩和变粒岩等变质岩组成,形成于中元古代[1]。岩群中片麻岩样品显示轻稀土元素富集的中等分异特征((La/Yb)N=4.71～7.97),斜长角闪岩具有平坦型((La/Yb)N=0.74～0.95)和轻稀土元素微弱富集型((La/Yb)N=1.06～3.63)两种稀土元素配分模式。在微量元素N-MORB标准化图解中,斜长角闪岩显示出洋中脊玄武岩和岛弧玄武岩的过渡类型特征。同时结合岩相学和岩石地球化学图解分析,推断片麻岩原岩为富含泥质的亚杂砂岩,而斜长角闪岩原岩为一套具有拉斑质到钙碱性过渡型特征的玄武岩;变质沉积岩形成于活动大陆边缘-大陆岛弧环境;变质基性火山岩形成于岛弧-弧后盆地。二者指示锡林浩特岩群形成于活动大陆边缘体系。 相似文献
17.
In this paper, we present data on major and trace elements in highly metamorphosed mafic rocks from the granulite-gneiss complex of the Angara-Kan block (southwestern Siberian craton), identify igneous protoliths of the metabasites, and assess the mobility of elements during metamorphism. Two types of rocks with different geologic relations and compositions were recognized. Garnet-bearing two-pyroxene granulites (Cpx + Pl + Grt + Opx) occur as sheet- and boudin-like bodies, which were folded and deformed with their host paragneisses. Dikes, which in most cases underwent only brittle deformation, are composed of metabasites characterized by the assemblage Cpx + Hbl + Pl + Grt. The major element compositions of igneous protoliths for the mafic granulites and metabasite dykes correspond to variously differentiated basaltic magmas. The protoliths of the metabasites are depleted in K2O, LILE, Zr, Nb, and LREE and were derived from a depleted mantle source. The major and trace element compositions of the dike metabasites are similar to those of low-K tholeiitic basalts of oceanic island arcs. Continental intraplate basalts derived from an enriched mantle source are possible igneous protoliths for the mafic granulites enriched in Ba, LREE, Nb, Ta, Zr, and Hf. It is assumed that lower Rb, Th, and U contents in the mafic granulites compared with continental flood basalts, high K/Rb and La/Th, and moderate Th/U ratios reflect the loss of Rb, Th and U during granulite-facies metamorphism. 相似文献
18.
John K. Zachariah V. Rajamani Gilbert N. Hanson 《Contributions to Mineralogy and Petrology》1997,129(1):87-104
The N–S trending, 2–4 km wide Ramagiri schist belt is made up of three blocks dominated by metavolcanic rocks, separated
and surrounded by granitic rocks of distinct characteristics. The metavolcanic rocks are tholeiitic in composition and are
very similar in their major element composition as well as in their abundances of some trace elements. However, the rare earth
elements (REE) require distinct sources. The rocks of the amphibolite facies eastern block have LREE depleted REE patterns
([Ce/Yb] = 0.7–0.9), requiring derivation from depleted mantle-like sources. The greenschist facies metatholeiitic rocks of
the central block have LREE enriched REE patterns ([Ce/Yb] = 3–6), reflecting the nature of their source(s). The Nd isotopic
data require that the LREE enriched nature could not have been attained significantly prior to its melting. The fine-grained,
upper greenschist facies metatholeiites of the western block have flat to slightly LREE depleted patterns ([Ce/Yb] = 0.8–0.95).
Minor fractional crystallization of rock forming minerals may relate a few samples to each other among samples from each of
the three blocks. Different extents of partial melting of distinct mantle sources have played a dominant role in the generation
of the parent magmas to the central versus eastern and western block metatholeiites.
The geochemical data suggest that the mantle sources were non-lherzolitic, and that these sources may have seen previous episodes
of melt addition and extraction prior to melting that gave rise to the parent melts to the rocks ∼2750 Ma ago. The REE data
indicate that while the sources of the eastern and western block rocks were similar to depleted mantle (ɛNd(
i
) about +2), the source of the central block rocks (ɛNd(
i
) about +3.5) were enriched in large ion lithophile element (LILE)-rich fluids/melts probably derived from subducting oceanic
crust. This and other trace element signatures point to magma extraction in tectonic settings similar to modern island arcs.
Subsequent to magma emplacement and crystallization, all the three suites of rocks were affected by interaction with low-temperature,
crustal derived fluids (ɛNd 2750Ma of about −8 to −12), probably during the accretion of the three blocks of the belt in the present form. The inferred source
characteristics, tectonic setting of magma generation and the crustal fluid processes seem to suggest that Phanerozoic-style
tectonic processes may have been important in the generation of Archean crust in the Dharwar craton.
Received: 31 July 1995 / Accepted: 12 May 1997 相似文献
19.
The study provides new petrologic and isotope geochemical data for rocks of the 465 ± 5 Ma Bulka massif (Borodina et al., 2011). The primary amphibole from granitoid stocks cutting across the layered series of the massif yielded an Ar–Ar age of 415.9 ± 3.7 Ma. The rocks of the Bulka massif have 143Nd/144Nd ratio of 0.513243 and εNd (Т) values of +12.00. The granitoids have 143Nd/144Nd ratios between 0.512919 and 0.512961 and εNd (Т) values between +8.03 and +9.25. The Nd isotope composition indicates that the rocks of the Bulka massif and granitoids were derived from a depleted mantle source. Depletion of the rocks of the massif in LILE, LREE, and HFSE over LILE is inherited from the mantle source, which has geochemical signatures of N-MORB and subduction-related components. Granitoids are metaluminous I-type granites, which were probably generated either by differentiation of intermediate to mafic mantle-derived magmas or by melting of metabasites. The rocks of the granitoid stocks are characterized by enrichment in LILE and LREE and depletion in HFSE over LILE, which suggests derivation from arc-related parental magmas. 相似文献
20.
Discovery and Geological Significance of Neoproterozoic Metamorphic Granite in Jimo, Shandong Province, Eastern China 总被引：1，自引：1，他引：0
ZHU Decheng Lü Dawei SHEN Xiaoli YANG Qing LI Dandan REN Tianlong YANG Shipeng 《《地质学报》英文版》2016,90(6):2080-2096
During the 1:50000 regional geological survey in Jimo,east Shandong Province,Paleoproterozoic metamorphic supracrustal rocks and Neoproterozoic metamorphic plutonite were newly discovered. These rocks displayed inclusions which had occurred in the Mesozoic granite,and the main lithologies are schist,granulite,marble,and granitic gneiss. Geochemical analyses suggest that Neoproterozoic metamorphic plutonite are characterized by high-K,metaluminous to weakly peraluminous. They are enriched in LILE and depleted in HFSE,with moderately enrichment of LREE,weak fractionation of LREE from HREE and negative Eu anomalies. The surface age of plutonic rocks in the survey area is 770.2±2.4 Ma,representing the age of magma crystallization,which is agreement with the the Neoproterozoic magmatic event after Rodinia supercontinent in the northern margin of Southern China continental block. In addition,the age of sporadic distribution(298 Ma and 269 Ma) is mixed zircon age,representing the rocks experienced metamorphism in Indosinian period. According to the associated mineral assemblages,and the characteristic metamorphic minerals and temperature pressure conditions,four metamorphic facies were identified,including amphibolitic,epidote amphibolite,greenschist,and mid-high pressure greenschist. Analysis of tectonic setting suggests that granitic gneiss is formed in an extensional environment and was involved from the continental margin magmatic arc to intraplate environment. Jimo is distributed in the east of Zhuwu fault,and has the same Spatial distribution location with the Weihai uplift UHP metamorphic belt rocks. The metamorphic rocks in Jimo area have similar geochemical characteristics of elements,tectonic setting and retrograde metamorphism with that in the Sulu UHP metamorphic belt. Therefore,Zhuwu fault may be the boundary fault of Sulu UHP metamorphic belt. 相似文献