浙江花岗岩类地球化学与地壳演化——Ⅱ.元古宙花岗岩类

浙江元古宙花岗岩类包括神功期（1．8－1．9Ga）和晋宁晚期（0．6—0．9Ga）。研究了浙江元古宙花岗岩类的主元素、微量元素、稀土元素和Rb、Sr同位素组成特征及岩石成因，探讨了浙江地壳的演化。浙江地壳形成于太古亩和元古宙，地壳增生的时期为2．6－2．7、0．8-1．1和0.1－0.12Ga。随时间演化浙江地壳组成有变化，但分异演化不明显。沿江-绍断裂分布的晋宁晚期慢源和壳幔混合中酸性岩是普宁期俯冲碰撞的证据。加里乐和印支期是两次规模不大的构造运动。     

济南城市四维动态地质信息系统构建研究

近20多年,济南泉水流量逐渐衰竭,泉水断流时有发生,为保护泉水,恢复泉水喷涌,塑造济南城市形象,该次研究基于50多年的济南地下水勘查、试验和研究成果,实现对城市多源、海量、多期次、多比例尺、异构地质数据的有效管理,然后建立不同地质数据的专业模型,实现对模型时空展布特征的三维可视化再现,并提供对模型的专业处理与分析。最后,从二维三维等水文地质概念模型出发,加入时间维度,由历史积累的时空关系,反映济南城市地下水的时空变化规律,在三维地质模型的基础上实现地下水动态监测数据的嵌入,构成地下水四维地质信息系统,在其空间表征的基础上,介绍了城市地下水的形成,泉水的分布、成因、演化以及泉水断流的原因、保泉供水的对策措施等,引导城市地下水的保护和发展,为政府决策提供参考。     

第五届东南亚及西太平洋钨锡花岗岩国际讨论会

1988年10月15—23日,在日本松江市和南朝鲜汉城举行第五届东南亚及太平洋钨锡花岗岩国际讨论会,来自澳大利亚、加拿大、英国、法国、西德、日本、泰国、马来西亚、越南、苏联、美国、南朝鲜、阿根廷和中国(10人)的120名代表出席会议。     

阿尔泰花岗岩类型与成岩模型的REE及O、Pb、Sr、Nd同位素组成依据

根据 REE 分布模式和 O、Pb、Sr、Nd 同位素组成特征,采用构造环境、物质来源和形成方式等多级标准,将阿尔泰花岗岩类划分为两个系列、五种类型,即造山花岗岩系列(阿尔泰系列),包括:壳-幔同熔型(青格里型),地壳交代型(额尔齐斯型),地壳重熔型(尚可兰型);非造山花岗岩系列(乌伦古系列),包括:幔源分异型(布尔根型),幔     

国外稀土元素地球化学的进展

稀土元素地球化学是一门新成长起来的学科。近几年来,国际上不仅有许多关于稀土元素地球化学的专门论述发表,而且在许多研究岩石成因、前寒武纪地质、地壳演化、天体化学、海洋化学、年代学方面的论述也多引用稀土元素地球化学证据。因正,Haskin(1984)在评价稀土元素地球化学的发展时写道:“目前,稀土元素地球化学已成为地球化学研究中     

Sm—Nd and Zircon U—Pb Isotopic Constraints on the Age of Formation of the Precambrian Crust in Southeast China

Nd model ages(TDM) of the Pre-Mesozoic crustal rock samples from Southeast China range from 1.2 to 3.5Ga.Two age peaks of 1.4Ga and 1.8 Ga are observed in the histogram of TDM model ages.Available U-Pb zircon inheritance ages are concentrated around 1.2-1.4Ga,1.8Ga and 2.5Ga,respectively.The combined use of Sm-Nd and U-Pb zircon inheritance ages suggests that the formation of the Precambrian curst is of episodic character.The oldest crustal nucleus may have been formed during the Late Archean(2.5Ga or older?).A rapid production of the crust took place 1.8 Ga ago,consistent with the global crust formation event at 1.7-1.9Ga.Another important episode of the addition of juvenile crustal material from the mantle in Southeast China took place 1.2-1.4Ga ago,during which the pre-existing crust was strongly reworked and/or remelted.     

Rare-earth element mobility during ore-forming hydrothermal alteration: A case study of Dongping gold deposit Hebei Province,China

REE mobility during hydrothermal ore-forming processes has been extensively investigated in recent years and the potential of REE to provide information about ore forming processes has commonly been recognized.The Dongping gold deposit,which is located in northwestern Hebei Province,China,occurring in the inner contact zone of the Shuiquangou syenite complex,is spatially,and probably genetically,related to the syenite,the deposit was formed under the moderate to high temperature(220℃ to 320℃),weakly acidic to weakly alkaline,rather high fo2(lgfo2=-30～-34)environment.The REE study of the host rocks,altered wall rocks,ores and gangue minerals from the deposit suggests that the REEs have been mobilized and differentiated during K-feldspathization and silicification.The extremely altered syenite enveloping auriferous quartz vein shows positive Ce anomaly and larger LREE/HREE ratio than that of the unaltered syenite.The REE concentrations and patterns of the ores are determined by the ore types and mineral assemblages,LREE/HREE ratios in the gangue quartz and hydrothermal Kfeldspars are relatively low.The most significant observation is that the gangue quartz shows significant positive Eu anomaly,whereas the hydrothermal K-feldspars show less significant or no positive Eu anomaly at all relative to the primary feldspar in the unaltered syenite. It is evident that the REEs are mobile during K-feldspathization and silicification in the ore forming process.Weak to moderate K-feldspathization caused REE mobility without apparent differentiation with the exception of extreme K-feldspathization and silicification which resulted in significant depletion of HREE and Eu and relative enrichment of Ce.The REE,Y,U,Th and Au contents of the syenite decrease as the degrees of K-feldspathization and silicification of the rocks increase towards the auriferous quartz veins.As the ores were deposited under a rather oxidized environment,Ce^4 predominated over Ce^3 .The precipitation of the former in the form of CeO2 or absorpted onto the secondary mineral assemblage resulted in the inconsistent removal of the REE and the relative Ce enrichment in the strongly altered rocks.in contrast,Eu was present mainly in a low valence state (Eu^2 ).The geochemical differences from the other REE^3 and much less sites in the secondary minerals to accommodate the Eu released form the original minerals resulted in the enrichment of Eu in the fluids.The mobility and differentiation of REE and the coherent mobilities of Y,U,Th and Au also support the argument that the syenite is one of the source rocks for gold mineralization.The REE contents and patterns of the altered rocks enveloping the auriferous quartz vein could be used as a guide for locating ore veins in mineral exploration.     

新疆北部的两类埃达克岩

新疆北部有两类埃达克岩，一是俯冲型，形成于早、中泥盆世-早石炭世晚期（≥320Ma），包括了埃达克岩、富Nb玄武岩、高（富）Mg安山岩。第二类埃达克岩是底侵型，形成于中晚二叠世（≤280Ma）。第一类埃达克岩分布于西天山的阿拉套山、博罗科努山，中天山的骆驼沟和巴仑台，东天山的土屋-延东，阿尔泰山陆缘南富蕴-青河南，准噶尔盆地中部陆梁，克拉玛依等地。在阿尔泰陆缘南，苦橄岩与埃达克岩、富Nb玄武岩和高（富）Mg安山岩密切组合。第二类埃达克岩分布于西天山的阿吾拉勒山和东天山的三岔口，未发现富Nb玄武岩和高（富）Mg安山岩组合。俯冲型埃达克岩、富Nb玄武岩和高（富）Mg安山岩的高Sr低Y、Yb、富Eu及高εNd（t）（＋1．5～＋10．0），低（^87Sr／^86Sr）；（〈0．7070）的同位素组成，均一致表明其源区物质为洋壳板片，部分为地幔楔、弧前棱柱，产于岛弧环境；而底侵型埃达克岩源于底侵的幔源玄武质物质，形成于后造山环境。两类埃达克岩及其组合岩石的地质及地球化学特点，展示了中亚型造山在本区晚古生代陆壳增生作用的多样性：在增生构造过程上，有洋壳板片的斜俯冲、俯冲板片的撕裂、板片窗、俯冲剥蚀及玄武质物质的底侵作用等；在增生方向上，有洋壳板片的侧向斜俯冲，也有玄武质物质垂向上底侵于壳-幔边界；在增生物质上，有洋壳板片、地幔楔、受地幔楔混染的洋壳板片熔体，弧前棱柱、地幔楔受板片熔体交代后形成熔体及底侵的幔源玄武质物质。与两类埃达克岩有关，尤其是第一类埃达克岩及其组合岩石，在本区广泛发育了Cu、Au成矿作用，其中部分达到大型-超大型规模。因此．对埃达克岩及其组合岩石的识别及相关Cu、Au成矿作用的找矿勘探应予以足够重视。     

东坪式与正长岩类有关的金矿床成矿机理的同位素地球化学制约

东坪式金矿床产于华北地台北缘金矿成矿带的冀西北金矿集中区,构造上位于华北克拉通北缘深大断裂-尚义-赤城断裂的南侧。金矿床产于泥盆纪早期(386～410Ma)水泉沟正长岩杂岩体内及接触带附近,矿体分布受脆-韧性剪切断裂构造的制约。金矿成矿作用具有多期次的特点,成矿时代为燕山期(156～203Ma)。矿石类型主要为石英脉型、石英网脉 脉旁钾硅化蚀变岩型和钾硅化蚀变岩型,具有典型的碱性岩金矿的金-碲组合,(含)金矿物主要为自然金、碲金矿和碲金银矿。流体包裹体的 H、O 及 He 同位素研究表明,成矿流体为以大气降水主的混合热液流体并可能存在深源流体的参与。矿床的 S、Pb、Sr 和 Si 同位素组成表明,金矿成矿物质主要来源于正长岩杂岩体,部分源于太古宙桑干群变质岩和燕山期花岗岩。因此,东坪式金矿是由燕山期伸展构造环境下热液流体在上涌地幔及岩浆活动的热驱动下对泥盆纪早期形成的正长岩交代改造的产物。     

西藏南部聂拉木-岗巴地区奥陶纪-老第三纪沉积地层稀土元素地球化学

藏南特提斯喜马拉雅沉积岩带，从奥陶纪到老第三纪，发育了一套层序连续完整的海相沉积地层，很少有缺失，沉积总厚度达万米以上，是研究古生代以来地壳化学演化的理想剖面。剖面岩石主要由灰岩、砂岩，粉砂岩和页岩组成。按剖面厚度计算，灰岩、砂岩、