Chracteristics and formation setting of granodiorite in Zhalute County, Inner Mongolia

Based on field investigation and study of petrology, mineralogy, geochemistry and isotopic geochronology for the granodiorite, the authors discussed the formation setting of the granodiorite. The pluton is calci alkalic and peraluminous granite in which light rare earth elements (LREE) are intensively enriched, heavy rare earth elements are relatively poor, the ratio of LREE to heavy rare earth elements (HREE) is 7. 12, and the fractionation of REE is good. The pluton formed in late orogenic setting which is relatively steady.     

Zircon U-Pb geochronology and geochemistry of diorite dikes from Nancha ore deposit in Tonghua area of Jilin and its geological significance

The authors presented geochronology and geochemical data of diorites from Nancha gold deposit in Tonghua region,with the aim to constraining its formation age,magma source and tectonic setting.LA-ICP-MS U-Pb dating results of zircons from the diorites indicate that the rocks were formed in the Middle Jurassic( 171± 2 Ma,MSWD = 1.19).Geochemically,these rocks have Si O_2 concentrations of 52.52%--54.90%,K_2 O of2.14%--3.84%,Na_2 O of 3.17%--3.35%,Mg O of 7.43%--9.34% and high Mg~# of 68.57-72.57.These rocks are characterized by enrichment in large ion lithophile elements( LILE,such as K,Ba,Rb and Sr) and light rare earth elements( LREE),relatively depletion in high field strength elements( HFSE,such as Ta,Nb,Ti and Zr),and heavy rare earth elements( HREE).These characteristics suggest that primary magma of the rocks were derived from the partial melting of mantle with miner crustal contamination,which may related to partial melting of mantle wedge by addition of sediment melt from subducting oceanic crust.Based on former and present studies,the authors consider that the Nancha ore deposit high-Mg diorites were formed in compressional structural setting which is similar to volcanic arc.It could be related to the subduction of the Paleo-Pacific plate beneath the Eurasian continent.     

Zircon U-Pb geochronology and geochemistry of Early Cretaceous granodiorite porphyries in Hutouya,western Shandong and their implications for petrogenesis

Zircon LA-ICP-MS U-Pb age and whole-rock geochemistry data are presented for the Hutouya granodiorite porphyries in Mengyin,western Shandong,to restrict its petrogenesis.The analyzed zircons exhibit oscillatory growth zoning and core-rim textures in the cathodoluminescence images and have high Th/U ratios( 0.04--1.66),indicating its magmatic origin.The youngest group of magmatic zircon yields weighted mean~(206)Pb/~(238) U age of 132 ± 2 Ma,which represents the forming age of the granodiorite porphyries,i.e.,the Early Cretaceous.The oldest group of magmatic zircon~(207)Pb/~(206) Pb ages ranges from 2 398 Ma to 2 370 Ma,yielding a weighted mean age of 2 389 ± 23 Ma,suggesting that the basement of the North China Craton should exist in the research area.Geochemically,the samples are characterized by high Si O_2( 70.38% and 64.87%),low Mg O( 0.60% and 1.53%) and Mg~#values( 42.92 and 50.42).Moreover,they show enrichment of light rare earth elements and large ion lithophile elements( e.g.Rb,Ba and K),depletion of heavy rare earth elements and high field strength elements( e.g.Nb and Ta),positive anomaly of Pb,and negative anomaly of Ti.These results,together with previously published data,indicate that the Hutouya granodiorite porphyries were derived from partial melting of a delaminated lower continental crust and subsequent interaction with the mantle peridotites.They are consistent with the period of lithospheric thinning beneath the eastern North China Craton and may be formed in an extensional tectonic environment.     

贵州大竹园大型铝土矿稀土元素地球化学特征及其意义

贵州大竹园大型铝土矿是中国近年来取得重要找矿进展的大型铝土矿之一。以采自大竹园矿区栗园向斜不同部位铝土矿、铝土岩和黏土岩的样品为研究对象,分析了这些样品的稀土元素含量(质量分数)特征及空间分布特征,研究了稀土元素含量与铝土矿质量及成矿过程的关系,最后就稀土元素对于成因和环境的指示意义进行了讨论。结果表明:铝土矿、铝土岩和黏土岩稀土元素总含量(不包括Y)分别为107.07×10-6、185.00×10-6和246.28×10-6,依次增高,说明铝土矿的成矿过程是一个稀土元素贫化的过程,也是Eu异常和Ce异常趋于增大的过程,即相对于黏土岩来说,铝土矿具有高Eu异常、Ce异常的特征;相对于重稀土元素来说,无论是栗园向斜西翼还是东翼,铝土矿轻稀土元素相对富集,且轻稀土元素含量以及La与Yb含量之比均随深度变浅而增加;单纯利用稀土元素图解不能有效反映成矿物质的来源,但可以大体反映含矿岩系形成于海相或海陆过渡相环境;大竹园大型铝土矿与黔北其他铝土矿一样,总体上属于沉积型,可能与古喀斯特化过程、古风化过程有关。     

新疆西准噶尔哈图岩体地球化学特征及其地质意义

哈图岩体侵位于西准噶尔南部早-中泥盆世海相火山-沉积地层中,主要岩性为二长花岗岩、正长花岗岩及少量碱长花岗岩,是研究西准噶尔晚石炭世构造环境的理想对象。哈图岩体花岗岩中SiO2含量(质量分数,下同)为72.06%~76.53%,全碱(Na2O+K2O)为7.80%~8.57%,CaO为0.20%~1.58%,MgO为0.07%~0.42%,明显具有高Si、富碱、贫Ca、低Mg的特征;这些花岗岩的Al2O3含量为12.55%~14.06%,A/CNK值为1.06~1.15,A/NK值为1.15~1.36,显示其为弱过铝质-强过铝质花岗岩。此外,哈图岩体具有较低的稀土元素总含量((88.14~139.53)×10-6)和高的轻、重稀土元素比值((La/Yb)N值为3.04~6.50),在球粒陨石标准化稀土元素配分模式中显示为典型的右倾"V"字形且具有强烈的负Eu异常,表明源区可能有斜长石残留或出现斜长石的分离结晶作用;在原始地幔标准化微量元素蛛网图中,这些花岗岩明显富集Rb、Th、U、K、Pb等大离子亲石元素,相对富集Zr、Hf,强烈亏损Sr、Ti、P,相对亏损Ba、Nb。以上特征及主量、微量元素特征和图解表明,哈图岩体为典型的弱过铝质-强过铝质A2型花岗岩,其形成于造山后伸展阶段,是由洋壳和岛弧组成的新生地壳受上涌的幔源物质加热,在浅部低压条件下发生部分熔融,再经分离结晶作用的产物。     

东昆仑东段坑德地区侵入岩岩石地球化学特征及其构造意义

对东昆仑造山带东段坑德地区出露的侵入岩进行了详细的岩石地球化学研究。结果表明,东昆仑造山带东段坑德地区岩体为一套高钾钙碱性花岗闪长岩,岩石由准铝质向过铝质过渡。岩石稀土元素具LREE元素富集、HREE元素亏损,有弱的负Eu异常的特征,微量元素明显富集大离子亲石元素(Rb,Ba,K)和活泼的不相容元素Th,U等;相对亏损高场强元素Nb,Ti,P;Rb/Sr,Nb/Ta,Zr/Hf等特征显示岩石具壳幔混合特征。岩石具有板块俯冲碰撞前活动大陆边缘构造环境特征,应该为阿尼玛卿洋向北俯冲碰撞过程中壳幔岩浆混合作用形成。     

Sedimentary environment of Late Carboniferous Tangjiatun Formation in Acheng of Heilongjiang

According to the lithological assemblages and elemental geochemistry of the measured Profile,the authors studied the sedimentary and tectonic environment of the Late Carboniferous Tangjiatun Formation ...     

西天山温泉布拉格达瓦一带托斯库尔他乌组沉积特征及构造环境分析

西天山温泉地区广泛发育泥盆—石炭纪火山—沉积地层,布拉格达瓦一带出露的托斯库尔他乌组发育一套由滨海间夹陆相—滨浅海相—浅海相过渡的碎屑岩夹火山碎屑岩的沉积建造,沉积物源主要为中酸性火山岩,碎屑颗粒沉积速度较快,属于近源沉积,蚀源区构造环境具活动性质,形成于未切割的活动岛弧。火山岩呈夹层、透镜体状分布于托斯库尔他乌组地层中,火山作用具周期性间歇喷发的特征,岩相表现为爆发—喷溢—沉积—爆发—沉积—爆发的周期性特点。火山岩属钙碱性岩石系列,火山岩浆对应的俯冲深度为上地幔。火山岩微量元素Nb,Sr,P,Ti,Ba为亏损型,Th,Zr元素富集,与岛弧环境密切相关;Nb/Ta为11.96~15.19,略低于原始地幔值,Zr/Hf为30.17~38.20,与原始地幔值相近。稀土总量∑REE为(186.57~208.58)×10^-6,轻重稀土比值为5.38~6.13;(Ce/Yb)_N为3.90~4.48,(La/Yb)_N为4.67~6.70,δEu为0.28~0.49,属于轻稀土富集型,显示为负铕异常。根据沉积物源区分析及主、微量元素特征,结合区域构造背景,认为晚泥盆世托斯库尔他乌组沉积建造所反映的构造环境为消减带俯冲碰撞的岛弧环境。     

乳山胡家口金矿中基性脉岩成因及与金矿化关系

胡家口金矿是牟平-乳山金成矿带内一小型矿床,研究程度低。该文对胡家口金矿区及外围发育的中基性脉岩进行岩石学和地球化学研究,进一步探讨脉岩与金矿化的关系。研究表明,胡家口金矿及外围发育的中基性脉岩主要为煌斑岩和辉石闪长玢岩。主量元素显示,二者总体属玄武质安山岩;微量元素方面,二者均富集大离子亲石元素和轻稀土,而亏损高场强元素;稀土元素总量高,表现为轻稀土富集,重稀土亏损的右倾特征。综合研究认为,中基性脉岩(尤其是煌斑岩)和金矿化都属于幔源C-H-O流体分异演化不同阶段的产物。     

南秦岭龙王洞地区中生代云峰寨单元花岗岩地球化学特征及其地质意义

该文对南秦岭龙王洞地区中生代云峰寨单元花岗岩的主量元素特征、微量元素特征及稀土元素特征进行分析研究,对该岩体进行较为全面的地球化学特征总结。研究表明:云峰寨单元花岗岩属于碱性过铝质A型花岗岩,形成于高温、贫水、高压的相对还原环境。花岗岩成因以地壳作用为主,花岗岩中稀土元素总体富集且分馏程度较高,轻稀土元素较重稀土元素富集且分馏明显。花岗岩为主动就位机制,是在早燕山期造山垮塌阶段的张性构造环境时期产生,与陆壳增厚、地幔物质减压隆升密切相关。     

南堡凹陷古近系沙河街组沉积环境和物源:来自微量和稀土元素地球化学的证据

为深入认识南堡凹陷沙河街组富有机质泥页岩形成机理,通过详细分析微量和稀土元素地球化学特征,对其水体沉积环境及物源进行研究。结果表明：微量元素Li, Cs, Bi较为富集;Cr, Sn较为亏损;其他微量元素接近于上地壳元素含量。稀土元素总量变化范围宽泛,接近或高于大陆上地壳的平均值,指示陆源碎屑供给较为充足。REE分配模式表现为轻稀土元素富集,分异程度较高;重稀土元素相对亏损,分异程度较低。铕元素异常值(δEu)负异常明显,铈元素异常值(δCe)基本正常。根据锶丰度和锶/钡比值的变化,反映出沙三段沉积时期湖泊水体具有一定的分隔性,淡水、半咸水和咸水环境共存;沙一段沉积时期湖泊水体的连通性增强,以半咸水环境为主。根据V/(V+Ni)、Th/U比值及δCe、铈异常指数(Ce_anom)值特征,反映出湖泊水体为分层较强的贫氧环境。源生Ba含量揭示出湖泊水体古生产力较高。通过稀土元素组合特征分析,认为沙河街组物源主要来自燕山褶皱带于燕山期发育的花岗岩,且混有少量沉积岩。南堡凹陷沙河街组泥页岩有机质富集程度与其古环境和古地理密切相关：一是适宜的水体古盐度和丰富的水体营养物质适应...     

Mechanisms and Processes Leading to Reverse Zoning in the Andong Granitoid Pluton, Andong Batholith, Korea

The Andong pluton consists of comagmatic granitoid rocks which constitute outstanding examples of reversely zoned granitoids. The pluton has three lithofacies: hornblende biotite tonalite, biotite granodiorite and porphyritic biotite granite. The zoned pattern forms by locating a tonalite core containing high-temperature mafic assemblages in central part,granodiorite rims in marginal part, and a porphyritic granite cap containing more felsic assemblages in topside of the pluton.Mineral abundances as well as bulk compositions of the granitoids indicate that the interior is enriched in mafic minerals and that it shows higher contents of oxides than the margin and topside. The compositional gradients change gradually with continuity between the lithofacies. The regular compositional variations within the pluton support the argument that the pluton behaved as an individual petrochemical system. Model abundances of the granitoids are in agreement with the bulk compositional gradients, suggesting that no significant interaction with country rocks occurred. Remobilization (resurgence) of deeper parts of the system into the more felsic magmas of the chamber explains the reverse zoning. Fractional crystallization was of importance and probably accounts for the selective removal of the settling phases. The Andong pluton is an example of reversely zoned plutons related by remobilization of more mafic but consanguineous magmas. Large-scale upwelling occurred in the pluton leading to the present arrangement of three lithofacies. It is conceivable that remnants of the reverse zoning become more difficult to discern as the plutonic rocks reach the latest stages of their evolution. In this case, the Andong pluton represents an earlier stage in the evolution of a felsic system that is usually represented by the final stages in normally zoned plutons.     

Reconstruction of protoliths of metamorphic rocks and tectonic setting of Wolegen Group

Parametamorphic rocks from Arong County in southeastern Inner Mongolia-Daxinganling district are regarded as Proterozoic in age,belonging to the Wolegen Group and composed of volcanoclastic and sandstone in origin,and have been disputed in tectonic setting.Because of the stability in metamorphism,the rare earth dements indicate the features of their protoliths.The authors integrated the petrologic methods with the geochemical parameters which include ∑REE,∑LREE/∑HREE,δCe,δEu,La/Yb,Sm/Nd,Th/Sc and the standard values of chondrite.The results show that the protoliths of Wolengen Group may be a group of voleanoclastic and continental margin elastic rocks,and their tectonic setting is the continent island arc.     

柴北缘布衣坦乌拉山南东段桑格斯帕地区变质侵入体地质特征及成因探讨

变质侵入体主要分布于桑格斯帕地区,是从达肯大坂岩群中剔除的一套变质侵入体,和达肯大坂岩群一起构成欧龙布鲁克微陆块的变质基底。变质侵入体常量元素属高分异铝过饱和钾玄岩、高钾钙碱性系列岩浆岩;微量元素显示岩石具火山弧花岗岩特点;稀土元素总体显示轻稀土较为富集、重稀土相对亏损。变质侵入体属于古元古代晚期因不同块体碰撞形成的具有挤压环境特征的火山弧花岗岩。     

青海省乌拉斯太地区早石炭世花岗质岩体地球化学特征及其地质意义

早石炭世花岗质岩体主要沿昆中断裂带两侧断续分布,多呈岩床、岩株状产出,根据岩性特征可划分为3类,即浅肉红色斑状二长花岗岩、肉红色正长花岗岩、肉红色中细粒碱长花岗岩.主量元素特征显示花岗质岩体全碱含量较高,显示出壳源的特点,为过铝质偏铝质花岗岩,属Ⅰ型花岗岩.稀土元素特征显示岩石属轻稀土富集型,重稀土相对平坦,轻重稀土分...     

Petrogenesis of Paleoproterozoic diorite porphyries in Luojiazhuang,western Shandong:constraints from LA-ICP-MS zircon U-Pb geochronology and geochemistry

Based on the study of LA-ICP-MS zircon U-Pb geochronology and whole-rock geochemistry for the Luojiazhuang diorite porphyries in Menying,western Shandong,the analyzed zircons exhibit oscillatory growth zoning in the cathodoluminescence images and have high Th / U ratios( 0. 15--1. 53),indicating a magmatic origin. In addition,most of the zircons have narrow metamorphic edges,suggesting that late metamorphic events may exist. The youngest group of magmatic zircon207 Pb /206 Pb ages ranging from 2 384 Ma to 2234 Ma,yielding a weighted mean age of 2353 ± 14 Ma,which represents the forming age of the diorite porphyries,as the Early Paleoproterozoic. Geochemically,the samples are characterized by low SiO_2( 54. 54% and 55. 47%),high MgO( 5. 22% and 5. 49%) and Mg~#values( 58 and 59). Moreover,they show enrichment of light rare earth elements and large ion lithophile elements( Rb,Ba and K),depletion of heavy rare earth elements and high field strength elements( Nb,Ta,Zr and Hf),positive anomaly of Pb,and negative anomaly of Ti. The fact implies that the Luojiazhuang diorite porphyries might derive from partial melting of enriched lithospheric mantle and mixed with an amount of continental crust material. In summary,they may form in the compression tectonic setting that stretching along the east-west direction at the North China Craton in the Early Paleoproterozoic.     

莱西塔埠头稀土矿氟碳铈矿Th-Pb定年及矿床成因

山东莱西市塔埠头稀土矿为一小型伟晶岩型稀土矿床,具有较好的找矿前景。该文通过对塔埠头稀土矿床地质特征、氟碳铈矿物的Th-Pb定年、成矿要素等的综合分析研究,确定了其成矿时代,建立了成矿模式,讨论了矿床成因。研究指出,塔埠头稀土矿床为小型伟晶岩型稀土矿床,主要稀土矿物氟碳铈矿包裹于长石中,2个样品获得的氟碳铈矿Th-Pb加权平均年龄为(128.5±2.0)Ma和(134.4±1.2)Ma。将塔埠头稀土矿成矿要素划分为4个必要要素、3个重要要素,认为在伟晶岩侵入到围岩的降温冷却过程中,形成了塔埠头中生代稀土热液成矿事件。     

江西赣州隆木花岗岩体年龄、成分特征及其构造意义

为了查明江西赣州隆木花岗岩形成时代及演化过程,对隆木岩体中的黑云母花岗岩与似斑状黑云母二长花岗岩进行LA-ICP-MS锆石U-Pb定年和同位素地球化学研究。结果表明:黑云母花岗岩与似斑状黑云母二长花岗岩的锆石U-Pb定年结果分别为(457±6)、(450±9)Ma,表明岩体形成于晚奥陶世;岩体铝饱和指数为1.11～1.29,K2O与Na2O含量(质量分数)之比为0.97～1.51,属强过铝质及高钾钙碱性岩石;根据ACF图解,岩体投影于S型花岗岩区域内;岩体Rb、Th+U、La+Ce、P、Nd、Zr+Hf+Sm相对富集,而Ba、Nb、Sr、Ti相对亏损,总体上属于低Ba、低Sr的花岗岩;岩体Rb与Sr含量之比为0.60～2.82,平均值为1.68,明显高于大陆地壳与上地壳的平均值,具壳源花岗岩特征;根据A/MF-C/MF图解,岩体物源区为砂质岩;岩体稀土元素含量总量偏低,为(113～176)×10-6,轻稀土元素富集明显,配分模式明显呈右倾型,Eu异常为0.38～0.67,Eu亏损程度中等偏高;化学成分显示,岩体属于强过铝质高钾钙碱性S型花岗岩,是一种壳源花岗岩,岩浆源区为成熟上地壳的砂质岩源区;构造判别图解、年龄信息及野外特征表明,岩体形成于后碰撞伸展构造环境。总之,隆木岩体形成于早古生代晚期的加里东构造运动,是华夏古陆块与扬子古陆块在新元古代碰撞拼贴之后裂解、在中奥陶世再次发生陆内碰撞使得地壳加厚部分重融、造山后期地壳伸展减薄、熔融物质上升侵位形成的岩体。     

山东蒙阴金伯利岩带地球化学特征和源区性质

通过主量、微量和稀土元素对山东蒙阴地区的3个金伯利岩带的金伯利岩、辉绿岩、煌斑岩地球化学特征进行分析研究。结果表明,金伯利岩的岩性偏碱性且富钾,K₂O、TiO₂、P₂O₅比一般的超基性岩石含量明显高;微量元素中Ba、Th、Ta、Cr、Ni元素含量明显高,Sr和Y、Yb含量相对原始地幔偏低。金伯利岩稀土元素总量偏高、轻稀土富集,重稀土亏损。总体无明显的Eu负异常。暗示了深部地幔成因的金伯利岩岩浆分异程度较低,基性程度相对高,岩浆混合了深部的榴辉岩和相对较浅的地幔橄榄岩,可能存在二辉橄榄岩和榴辉岩、花岗质等包体捕掳体来源的混杂性。从地幔深部的高温高压的环境下,金伯利岩岩浆携带深部的金刚石矿物捕掳体沿辉绿岩侵位通道侵入上涌,在接近地表,温压骤降,岩浆岩隐爆就位,最后形成常马、西峪、坡里三个金伯利岩带。     

广西大化县透闪石玉的产地特征

广西河池市大化瑶族自治县发现了透闪石玉矿床,研究程度较低,但是该产区玉石在市场上却占有不小份额,对该区透闪石玉的宝石学特征及其产地属性进行系统研究具有重要意义。通过常规测试、拉曼光谱（RAMAN）、X射线粉晶衍射（XRD）、电感耦合等离子质谱（ICP-MS）、激光诱导击穿光谱（LIBS）等测试,研究该区透闪石玉的包体特征、谱学特征、结构特征和成分特征,来解读本地区透闪石玉的产地属性。研究结果显示:大化透闪石玉的主要矿物成分SiO₂、MgO和CaO较为稳定,次要矿物成分MnO,FeO,TiO₂的变异系数相对较大,样品的微量元素B,Cr,Zn,Sr含量较高,V,Co,Ni的含量相对较低,Fe2+/（Mg2++Fe2+）平均值为0.03,显示主要矿物为透闪石,说明本区透闪石玉为镁质大理岩受到接触交代变质作用而形成,低铁,高钙为特征;从样品所含有的稀土元素来看,该矿区的透闪石玉稀土元素总量∑REE偏低,轻重稀土元素分异不明显,属于轻稀土元素富集型,稀土配分模式属于右倾型,比较平坦,Eu负异常,有明显的Ce负异常;透闪石玉结晶度平均值为0.963,大于新疆透闪石玉的结晶度平均值0.843,与青海的0.96相近,这反映出大化透闪石玉的结晶程度较高,晶体颗粒相对较大,结晶环境良好;透闪石玉中铍/硅LIBS强度比（I_Be/I_Si）为:中国广西大化透闪石玉为0,中国新疆透闪石玉0.003~0.008,中国青海透闪石玉为0,中国辽宁透闪石玉为0.004~0.006,韩国透闪石玉为0.1~0.16,俄罗斯透闪石玉为0.03~0.05。研究结果与其他产地的比对可为溯源提供参考。