单接收稀有气体质谱仪由于效率、测试精度相对较低,制约了高精度40Ar-39Ar测年的进一步发展.近年来,新一代多接收稀有气体质谱仪在高精度40Ar-39Ar测年中显示出巨大的优势和潜力,并得到了日益广泛的应用.简要介绍了基于多接收稀有气体质谱仪Argus VI的激光全熔/阶段加热40Ar-39Ar测年实验技术,并对空气氩同位素、标准样品FCs和YBCs以及东昆仑开木其花岗岩体钾长石样品开展了测试研究.结果显示,连续4个月326次循环测试得到的空气氩同位素比值及对应的质量歧视因子(MDF)十分一致,显示了仪器系统良好的稳定性;FCs与YBCs单颗粒全熔"模式年龄"结果表明,仪器在单颗粒、微量样品测试中具有良好的测试精度,"模式年龄"精度可以达到1‰以下(不含衰变常数及标准样品年龄误差);FCs的单颗粒全熔测试获得的J值及F值(40Ar*/39ArK)与萨尔茨堡大学ARGONAUT实验室结果具有相同的变化趋势,均反映了捷克LVR-15反应堆中子通量的梯度变化;对YBCs单颗粒全熔测试获得YBCs与FCs之间的内部校正系数RYBCsFCs=1.045304±0.000752(1σ),YBCs单颗粒全熔年龄为29.280±0.086(1σ),与前人结果在误差范围内一致.对东昆仑开木其花岗岩钾长石激光阶段加热测试,得到其坪年龄为229.9±0.2 Ma(1σ,MSWD=1.59),反等时线年龄为229.8±0.4 Ma(1σ,MSWD=1.71).综合区域内已有锆石U-Pb年代学及黑云母、钾长石40Ar-39Ar年代学研究成果,认为开木其岩体钾长石40Ar-39Ar年龄反映了东昆仑晚三叠世的一次快速冷却-剥露过程.

东亚大陆是由许多分别亲劳亚或亲冈瓦纳的中小陆块经过复杂拼合而成的最为复杂的大陆,而中国大陆地处东亚的核心位置,是研究东亚大陆形成演化的关键.控制中国大陆形成演化的最主要的构造格架是“十字构造”,即东西向的中央造山系和南北向的贺兰—川滇南北构造带.前者自东而西包括秦岭造山带、祁连造山带和昆仑造山带,是南方和北方陆块群历经古生代—印支期拼合形成中国大陆主体的构造结合带,并遭受中新生代陆内造山改造,构成了中国大陆地质地理、生态环境、人文经济等南北分野;后者不同区段继承了前寒武纪板块构造记录,逐步转化为古亚洲洋或古特提斯构造域大陆边缘,尤其是新特提斯构造运动,形成青藏高原隆升—扩展变形的东部边界,控制了晚中生代—新生代中国大陆东西反转演化.以“十字构造”为坐标系,中国大陆四个象限的地质、地球物理结构、自然资源、生态环境、人文经济等存在明显差异.

贺兰山汝箕沟地区上三叠统延长组顶部发育一套基性火山岩,为我们探讨贺兰山地区晚三叠世的构造属性提供了重要依据.该套火山岩为一套拉斑玄武岩,主量元素以相对富Na2O(1.29％～ 3.66％)、贫K2O(＜1％)和低Mg#(43％ ～ 58％)为特征.稀土元素总含量较低(65.13×10-6～94.52×10-6),(La/Yb)N=3.46～4.71,为轻稀土富集型.富集Cs、Rb、Ba等大离子亲石元素和高场强元素,结合构造环境判别图解,该套火山岩形成于陆内裂谷环境.岩浆喷溢时间晚于盆地裂陷沉积时间,具被动裂谷性质.综合分析表明,汝箕沟玄武岩岩浆是拉张作用下岩石圈地幔尖晶石二辉橄榄岩与石榴石二辉橄榄岩过渡区域部分熔融的产物,并经历了一定程度的橄榄岩、单斜辉石的结晶分异,表明晚三叠世—早侏罗世阿拉善地块与东部华北板块之间曾经历过一次伸展裂解事件.

南秦岭大巴山城口断裂带出露一套玄武安山岩、安山岩组合,火山岩锆石LA-ICP-MS U-Pb定年测试结果为716±4Ma,表明其为新元古代岩浆产物;岩石地球化学研究表明火山岩富集轻稀土元素,原始地幔标准化微量元素蛛网图显示以富集大离子亲石元素Cs、Ba、Th、U及高场强元素分异为特征,Nb、Ta强烈亏损以及低的Ti(TiO2 ＜0.85％)含量,与典型的岛弧火山岩相似;微量元素La/Nb、Th/Yb及Hf/Ta比值特征也显示岛弧岩浆属性,相对高的Zr/Y、Ta/Yb和低的Zr/Nb比值区别于大洋岛弧火山岩,具有明显的大陆亲缘性,表明城口火山岩形成于陆缘岛弧环境.综合已有的地质、地球化学及同位素年代学研究表明新元古代晚期扬子板块北缘及南秦岭地区为一活动陆缘岩浆杂岩弧,暗示中国华南板块很可能位于Rodinia超大陆的边缘部位.

The X-ray Fluorescence Spectrometry (XRF) method was adapted for the determination of 10 major elements, such as silicon, aluminum, calcium and magnesium, in different types of rocks. The calibration curves were determined from 28 different types of rock standards which were fused into glass beads. The matrix effect was calibrated by using empirical factors. This method was used for determining the 10 major elements of samples from GeoPT proficiency testing. The 23 types of rock samples were analyzed over 15 years and the results indicate that this method is most effective in determining SiO2, Al2O3, K2O and CaO with the obtained|Z| < 2 for all samples. This method is also suitable for determining MgO, MnO, TiO2 and Na2O although each element has only one suspect result in different samples with the obtained|Z|>2, which was caused by the matrix difference between samples and standard samples in measuring the lower content elements. When the content of TFe2O3 is higher than 1.00% and P2O5 between 0.08% and 0.80%, the results can match expectations (the obtained|Z| < 2). To sum up, the developed XRF method has long term stability and is effective, which can match the expectation of applied geochemistry laboratories for determination of 10 major elements in different types of rock samples.

秦早期青铜器是早期秦文化的重要组成部分,在秦人早期生活的地区没有发现古铜矿和铅矿遗址,所以关于秦早期青铜器的矿料来源至今仍是一个谜.本文利用铅同位素比值分析方法探讨秦早期青铜器中铅矿料的来源,结果表明,秦早期青铜器使用的铅料很可能就来自秦岭山带.

The tectonic evolution of southern Khanka block is very complex,and there is not enough of the precise chronological evidence and systematic geochemical studies.Zircon U-Pb dating results show that the granites from southern Xingkai block were intruded at the end of Late Triassic (202-205 Ma)in a transition stage of paleo-Asian Ocean and paleo-Pacific tectonic system.It is found that the monzonitic granites and granodiorites are all characterized with enriched silicon (SiO2 =69.61%-77.27%),weakly supersaturated aluminum (Al2 O3 =12.70%-15.28%)and relatively enriched potassium (AKI=0.64-0.88),which indicates that the granites are fractionated I-type granites,taking into account of the presence of amphibole and low zircon saturation temperature (TZr=679-787 ℃).176 Hf/177 Hf ratios are high (0.282 773-0.282 913);εHf (t)is positive (4.39-9.32),and two-stage Hf model ages are young (0.65-0.96 Ga),which shows that its source material is from the depleted mantle of new-born young crust of Neoproterozoic.It is concluded that the granite was formed in the context of the initial western Pacific subduction into active continental margin based on the age of the rock formation,and other rock features.

LA-ICPMS zircon U-Pb dating has been greatly advanced and widely applied in the past decade because it is a cheap and fast technique. The internal error of LA-ICPMS zircon U-Pb dating can be better than 1%, but reproducibility (accuracy) is relatively poor. In in order to quantitatively assess the accuracy of this technique, zircons from two dioritic rocks, a Mesozoic dioritic microgranular enclave (FS06) and a Neoproterozoic diorite (WC09-32), were dated independently in eight laboratories using SIMS and LA-ICPMS. Results of three SIMS analyses on FS06 and WC09-2 are indistinguishable within error and give a best estimate of the crystallization age of 132.2 and 760.5 Ma (reproducibility is ∼1%, 2RSD), respectively. Zircon U-Pb ages determined by LA-ICPMS in six laboratories vary from 128.3±1.0 to 135.0±0.9 Ma (2SE) for FS06 and from 742.9±3.1 to 777.8±4.7 Ma (2SE) for WC09-32, suggesting a reproducibility of ∼4% (2RSD). Uncertainty produced during LA-ICPMS zircon U-Pb analyses comes from multiple sources, including uncertainty in the isotopic ratio measurements, uncertainty in the fractionation factor calculation using an external standard, uncertainty in the age determination as a result of common lead correction, age uncertainty of the external standards and uncertainty in the data reduction. Result of our study suggests that the uncertainty of LA-ICPMS zircon U-Pb dating is approximately 4% (2RSD). The uncertainty in age determination must be considered in order to interpret LA-ICPMS zircon U-Pb data rationally.

鄂尔多斯西南缘地处北秦岭、北祁连、贺兰山构造带交接部位,构造带西段的南华山弧形构造带中发育有大量早古生代花岗岩体(岩株),侵入于下元古界海原群以及中寒武统香山群、下奥陶统阴沟群中.岩性以花岗闪长岩为主,其次为二长花岗岩和石英闪长岩,并有少量角闪奥长花岗岩和斑状花岗岩等,其中普遍含有暗色闪长质包体.地球化学研究表明,岩石主要为准铝-过铝质、钙碱性系列,具有明显高Al2O3、低MgO特征,尤其是低Y和Yb、高Sr和Sr/Y比值特征,类似于典型的埃达克岩地球化学组成.同时,岩石明显亏损Nb、Ta、P和Ti,富集Cs、Rb、Ba、Th、U、K、Pb、Nd、Zr等.综合分析认为,早古生代祁连俯冲洋壳板片熔融,熔体与楔形地幔熔体混合后上侵,并与下地壳熔体再次混合形成了南华山花岗岩.利用LA-ICPMS法测得花岗岩锆石U-Pb同位素年龄为416± 14 Ma,代表了花岗岩结晶年龄.综合利用区域地质、地层特征和不整合接触关系,限定祁连-秦岭交接区俯冲、碰撞造山和地壳加厚发生在志留纪末期.

通常将华南克拉通的形成理解为扬子陆块与华夏陆块于新元古代沿江南造山带的碰撞拼合,但对两陆块内部的组成和演化关系的了解却相对有限.通过对比神农架地区和扬子陆核区前寒武纪地层碎屑锆石的年龄结构及其原位Hf同位素组成特征,分析了扬子陆块西北部中元古代晚期一新元古代早期的构造演化规律,并对其与统一华南克拉通形成的关系进行了探讨.对前人数据进行统计和对比的结果表明,神农架群碎屑锆石年龄谱中记录了约1.6Ga的年龄峰值,且其原位Hf-O同位素分析指示该期岩浆事件存在幔源物质加入,而相应的岩浆事件(锆石)在扬子陆块陆核区(崆岭地区)前寒武纪地层或岩浆岩单元中缺乏记录.结合神农架群细粒沉积岩Nd同位素地层学特征,指示中元古代时期神农架地区位于活动大陆边缘的构造环境,且神农架群沉积地层的碎屑物质并非由扬子陆核区的崆岭基底岩系经风化一剥蚀作用提供,即非扬子陆核区的边缘盆地.这些证据说明,在新元古代以前,神农架地区与扬子陆核区之间属于两个独立的次一级微陆块.

The granites in southern Manzhouli region of Inner Mongolia are composed mainly of alkaline-feldspar,orthoclase and adamellite granite. We present new zircon U--Pb dating of granites using ablation LA--ICP--MS technique. The result shows that three stages of granites in the southern Manzhouli region: Middle to Late Triassic( 208 ~239 Ma),Early Jurassic( 179 ~185 Ma),Late Jurassic to Early Cretaceous( 137 ~151 Ma),which are consistent with all of the Da Hinggan Mountain,and this geochronological framework is also comparable to that in the Zhangguangcai-Lessor Hinggan Mountain in the East. Zircon Hf analyses conducted by LA--MC--ICP--MS show that these granites have eHf( t) values of +0. 7 ~ +9. 5 with Hf modal ages of 0. 6 ~1. 2 Ga,indicating that thecrust in the Ergun block was extracted from mantle during Meso-Neoproterozoic,which is different from the Xing'an block to the south,where the crustal accretion was aged in the Neoproterozoic-Phanerozoic.

We have undertaken major and trace element analyses of volcanic rocks in Northeast China, as well as U–Pb dating and Hf isotopic analysis of their zircons, in order to determine the petrogenesis and tectonic setting of the volcanics. Mesozoic volcanism in the southern Manzhouli area occurred in two stages: Middle to Late Jurassic (164–147 Ma) and Early Cretaceous (142–123 Ma). The first stage is represented by the Tamulangou, Jixiangfeng, and Qiyimuchang formations. The Jixiangfeng Formation (162–156 Ma) is a rhyolite–trachyte dominated unit that lies between two basalt units, namely the underlying Tamulangou (164–160 Ma) and overlying Qiyimuchang (151–147 Ma) formations. The second igneous stage is dominated by rhyolitic lavas and tuffs of the Shangkuli Formation and basaltic rocks of the Yiliekede Formation, and they yield zircon U–Pb ages of 142–125 and 135–123 Ma, respectively. Basaltic rocks of the Tamulangou and Yiliekede formations have a wide range of MgO contents (1.64–9.59 wt%), but are consistently depleted of Nb and Ta and enriched with incompatible trace elements such as large ion lithophile elements (LILEs) and light rare earth elements (LREEs). Trachytes and rhyolites of the Jixiangfeng and Shangkuli formations are characterized by enrichment in LILEs and LREEs relative to HFSEs and HREEs, and with negative Nb, Ta, P, and Ti anomalies and positive ϵ Hf(t) values (3.49–9.98). These data suggest that basaltic volcanic rocks in southern Manzhouli were generated by fractional crystallization of a common parental magma, which was derived by partial melting of metasomatized (enriched) lithospheric mantle, whereas the trachytic and rhyolitic magmas were produced by the melting of lower crustal mafic and felsic granulites, respectively. Geochronological data indicate that Mesozoic volcanism in southern Manzhouli was initiated in the Middle to Late Jurassic and continued into the Early Cretaceous. It was mainly induced by lithospheric extension after the closure of the Mongol–Okhotsk Ocean.

We conducted geochemical and isotopic studies on the Oligocene–Miocene Niyasar plutonic suite in the central Urumieh–Dokhtar magmatic belt, in order better to understand the magma sources and tectonic implications. The Niyasar plutonic suite comprises early Eocene microdiorite, early Oligocene dioritic sills, and middle Miocene tonalite + quartzdiorite and minor diorite assemblages. All samples show a medium-K calc-alkaline, metaluminous affinity and have similar geochemical features, including strong enrichment of large-ion lithophile elements (LILEs, e.g. Rb, Ba, Sr), enrichment of light rare earth elements (LREEs), and depletion in high field strength elements (HFSEs, e.g. Nb, Ta, Ti, P). The chondrite-normalized rare earth element (REE) patterns of microdiorite and dioritic sills are slightly fractionated [(La/Yb)n = 1.1–4] and display weak Eu anomalies (Eu/Eu* = 0.72–1.1). Isotopic data for these mafic mantle-derived rocks display ISr = 0.70604–0.70813, ϵNd (microdiorite: 50 Ma and dioritic sills: 35 Ma, respectively) = +1.6 and −0.4, TDM = 1.3 Ga, and lead isotopic ratios are (206Pb/204Pb) = 18.62–18.57, (207Pb/204Pb) = 15.61–15.66, and (208Pb/204Pb) = 38.65–38.69. The middle Miocene granitoids (18 Ma) are also characterized by relatively high REE and minor Eu anomalies (Eu/Eu* = 0.77–0.98) and have uniform initial 87Sr/86Sr (0.7065–0.7082), a range of initial Nd isotopic ratios [ϵNd(T)] varying from −2.3 to −3.7, and Pb isotopic composition (206Pb/204Pb) = 18.67–18.94, (207Pb/204Pb) = 15.63–15.71, and (208Pb/204Pb) = 38.73–39.01. Geochemical and isotopic evidence for these Eocene–Ologocene mafic rocks suggests that the magmas originated from lithospheric mantle with a large involvement of EMII component during subduction of the Neotethyan ocean slab beneath the Central Iranian plate, and were significantly affected by crustal contamination. Geochemical and isotopic data of the middle Miocene granitoids rule out a purely crustal-derived magma genesis, and suggest a mixed mantle–crustal [MASH (melting, assimilation, storage, and homogenization)] origin in a post-collision extensional setting. Sr–Nd isotope modelling shows that the generation of these magmas involved ∼60% to 70% of a lower crustal-derived melt and ∼30% to 40% of subcontinental lithospheric mantle. All Niyasar plutons exhibit transitional geochemical features, indicating that involvement of an EMII component in the subcontinental mantle and also continental crust beneath the Urumieh–Dokhtar magmatic belt increased from early Eocene to middle Miocene time.

Based on documented geochronological and whole-rock geochemical data, this paper reports for the first time the zircon Hf isotopic composition of the Shennongjia andesitic ignimbrite, with the purpose of constraining the magmatic source and petrogenesis. The results obtained by the authors reveal that the Nd-Hf decoupling occurs in the rocks. Although the samples have relatively constant elemental geochemical characteristics and Nd isotopic composition, highly variable zircon εHf(t) values (-24.0~+0.3) are existent in a single sample, corresponding to zircon Hf isotope model age (TDM) of 2587~1608 Ma and suggesting that terrestrial clastic components contamination occurred during the generation and upwelling of magma. Such a component evidently modified part of the zircon Hf isotopic composition during magma crystallization but did not affect the whole geochemical and Nd isotopic composition, revealing that the zircon in-situ Hf isotope was more sensitive to the clastic contamination than whole-rock Nd isotope during the formation and evolution processes of magma. Combined with whole-rock geochemical features, this paper points out that the Shennongjia andesitic ignimbrite might have been derived from Proterozoic mafic lower crustal anatexis caused by upwelling of mantle-derived magma, and experienced the contamination of subducted clastic rocks during its upwelling.

利用金相显微镜、电子扫描显微镜、能谱仪和多接收等离子体质谱仪对凤翔出土的青铜建筑构件以及相关文物进行了研究,发现:凤翔出土铜建筑构件含铜量在73％～83％之间,含锡量在10％～18％之间,含铅量在1％～10％,为铅锡铜三元合金；铜建筑构件的铅同位素关系图显示其与礼县几乎完全重合,涵盖了宝鸡县青铜器铅同位素比值分布范围,说明凤翔青铜构件系由秦人自己制作.

U-Pb dating and Hf isotopic analyses of zircons from various granitoids, combined with major and trace element analyses, were undertaken to determine the petrogenesis and geodynamic setting of Neoproterozoic and Late Paleozoic magmatism in the Manzhouli-Erguna area of Inner Mongolia, China. The Neoproterozoic granitoids are mainly biotite monzogranites with zircon U-Pb ages of 894 +/- 13 Ma and 880 +/- 10 Ma, and they are characterised by enrichment in large ion lithophile elements (LILEs; e.g., Rb, Ba, K) and light rare earth elements (LREEs), depletion in high field strength elements (HFSEs; e.g., Nb, Ta, Ti) and heavy rare earth elements (HREEs). The Late Devonian granitoids are dominantly syenogranites and mylonitised syenogranites with zircon U-Pb ages of 360 +/- 4 Ma, and they form a bimodal magmatic association with subordinate gabbroic rocks of the same age. The Late Devonian syenogranites have A-type characteristics including high total alkalis, Zr, Nb, Ce and Y contents, and high FeOt/MgO, Ga/Al and Rb/Sr ratios. The Carboniferous granitoids are mainly tonalites, granodiorites and monzogranites with U-Pb ages varying from 319 to 306 Ma, and they show very strong adakitic characteristics such as high La/Yb and Sr/Y ratios but low Y and Yb contents. The Late Permian granitoids are dominated by monzogranites and syenogranites with zircon U-Pb ages ranging between 257 and 251 Ma. Isotopically, the epsilon(Hf)(t) values of the Neoproterozoic granitoids range from +4.3 to +8.3, and the two-stage model ages (T-DM2) from 1.2 to 1.5 Ga. The Late Devonian granitoids are less radiogenic epsilon(Hf)(t) from +12.0 to +12.8 and T-DM2 from 545 to 598 Ma] than the Carboniferous [epsilon(Hf)(t) from +6.8 to +9.5 and T-DM2 from 722 to 894 Ma] and Late Permian granitoids [epsilon(Hf)(t) from +6.1 to +9.4 and T-DM2 in the range of 680-895 Ma]. These data indicate (I) the Neoproterozoic granitoids may have been generated by melting of a juvenile crust extracted from the mantle during the Mesoproterozoic, probably during or following the final stages of assembly of Rodinia as a result of the collision and amalgamation of Australia and the Tarim Craton; (2) the Late Devonian granitoids may have formed by partial melting of a new mantle-derived juvenile crust in a post-orogenic extensional setting; (3) the Carboniferous granitoids appear to have been produced by melting of garnet-bearing amphibolites within a thickened continental crust during and following the collision of the Songnen and Erguna-Xing'an terranes; and (4) the Late Permian granitoids may have been generated by melting of garnet-free amphibolites within the Neoproterozoic juvenile continental crust, probably in the post-collisional tectonic setting that followed the collision of the North China and Siberian cratons. (C) 2013 Elsevier Ltd. All rights reserved.

Zircon U Pb dating results show that the intermediate-basic volcanic rocks from Changling depression in the Songliao basin formed at Early Cretaceous,rangingd from 101 Ma to 116 Ma,which belong to Yingcheng Formation rather than Huoshiling Formation.Petrologically,the volcanic rocks are composed dominantly of olivine basalt and andesite,but geochemical data show that the volcanic rocks belong to alkaline series and are composed mainly of basalt,trachybasalt and basaltic trachyandesite.The intermediate-basic volcanic rocks have low contents of MgO and small Mg#(0.27 0.53);The chondrite-normalized rare earth element (REE)patterns indicate that the volcanic rocks show significant fractionation of HREE and LREE [(La/Yb)N = 6.60 10.96]and weak Eu anoalies&nbsp;(δEu=0.85 1.02);The trace element geochemistry are characterized by enrichment in large ionic lithophile elements and LREEs,weak positive anomalies in Nb,Ta,depletion in compatible elements (Cr,Co,Ni)and Rb,K.All of the samples display highly consistent REE patterns and trace elements spider diagrams with OIB.The magma source is situated in the asthenospheric mantle,and experienced deep mantle fluid metasomatism enrichment.These rocks were not accompanied by contamination of continent crustal materials during their magmatic evolution.

To determine petrogenesis and tectonic background of the early Mesozoic granites in the Sunwu-Jiayin area, Xiao Hinggan Mountains, U-Pb dating and Hf isotopic composition in zircon grains, major and trace element characteristics in different granites have been analyzed. Due to their zircon U-Pb ages, ages of granites in this area can be classified into two periods: the Late Triassic period (~210 Ma) and Early Jurassic period (187-181 Ma). Geochemical data indicate that the Late Triassic alkali feldspar granite belongs to the aluminous A-type granite, and was originated from partial melting of the newly accreted Neoproterozoic basic igneous crust. The Early Jurassic tonalite-granodiorite and monzogranite have similar geochemical characteristics as the adakite, and were formed by partial melting of the thickened lower crust. The Early Jurassic syenogranite and alkali-feldspar granite are of significantly different characteristics from the cotemporaneous adakite, and were derived from the basaltic crust accreted from depleted mantle during the Mesoproterozoic period. Combining with the regional researching results, it's suggested that the Late Triassic granite was resulted from the post-orogenic extension after the collision between the North China plate and Siberia plate, whereas the Early Jurassic granites formed in a compressive tectonic setting related to the subduction of the Pacific plate.

The trace elements in bronzes were collected from Lixian museum and Longxian museum in Gansu, Baoji museum and Fengxiang museum in Shaanxi were tested and analyzed by laser ablation inductively coupled plasma mass spectrometry.It was found that same material was used in different parts of the same bronze and bronze body and its supplements were also made of the same material.Based on the factor analysis no obvious difference in trace elements was found in bronzes between the four areas and this result might imply that ancient Qin people possessed independent mining and bronze manufacture skills and stable mineral resources. In addition,the character of laser ablation inductively coupled plasma mass spectrometry was a suitable method for trace elements analysis in the remaining body of bronzes.The results have enriched the Qin cultural research. Besides,the study also provides a new method for microanalysis of the trace elements in ancient artifacts.