东秦岭武关岩群的组成特征及其大地构造意义

东秦岭商丹地区的武关岩群是从原刘岭群北部分解出来的新的构造岩石地层单位,已获得其中变质基性火山岩Ｓｍ－Ｎｄ同位素年龄为（１３８２±３０）Ｍａ,原岩建造主体为碎屑沉积岩－碳酸盐岩－基性火山岩组合。变质基性火山岩及碎屑沉积岩的岩石地球化学特征表明,他们分别属于大陆板内拉斑玄武岩和大陆岛弧－活动陆缘型杂砂岩,因而武关岩群主体形成于中元古代晚期秦岭造山带拉张裂谷体制构造环境,于晋宁期（１０００～８００Ｍａ）的俯冲碰撞造山过程中拼贴于商丹构造带南侧。     

园子坪岩组与界河口岩群构造环境对比分析

通过对1:25万苛岚县幅区调修测和1:5万岚县测区矿调分析,认为吕梁山地区新太古代时期形成的界河口岩群是一套富铝的孔兹岩系夹基性火山岩的岩石组合,包括园子坪岩组、阳坪上岩组、贺家湾岩组。其中园子坪岩组为一套变质基性火山岩为主的岩石组合。通过对园子坪岩组中的变质基性火山岩的岩石特征、岩石化学、岩石地球化学特征的研究,探讨了界河口岩群形成的构造环境。     

佛坪地区中元古代孔兹岩系地质特征

根据佛坪地区广泛出露的一套副变质岩系的岩石组合、矿物组合、变质相特征和岩石地球化学特征的分析，认为它们是一套中深变质的碎屑岩－泥质岩－碳酸盐岩建造。原岩形成于相对稳定的大陆边缘－微板块内的陆表海环境。经过角闪岩相区域变质作用，形成了佛坪地区较为完整的孔兹岩系     

栾川群大红口组火山岩研究初探

河南省栾川群大红口组火山岩 ,岩性以碱性粗面质熔岩为主 ,经受不同程度的区域变质、动力变质及热液变质作用。喷发类型以裂隙式为主 ,有 4个喷发韵律 ,喷发环境为浅海 ;岩石地球化学特征显示 :其碱性火山岩属钾质型 ,形成于板内裂谷环境 ,与其伴生的辉长岩为同源岩浆成因 ,均来源于上地幔与下地壳的部分熔融产物     

浅析山西省原平市小里地铁矿矿床成因及找矿标志

五台群石咀亚群金岗库组为一套以火山岩为主的沉积变质岩系,沉积岩以杂砂岩为主,包括砂质泥岩和硅铁质建造.经区域变质作用与混合岩化作用,火山--沉积岩系岩石在温度、压力及化学活动共同作用下发生变质,使其中硅铁建造中的矿物发生变质分异重熔和重结晶作用,形成磁铁石英岩.多期次的构造运动,特别是褶皱构造的迭加改造,使铁矿层厚度加大,形成工业矿床.     

豫西高山河组云梦山组火山岩特点及其构造背景

位于华北板块南缘的高山河组、云梦山组碎屑岩系,是熊耳群火山岩系的第一沉积盖层,局部夹火山岩层。火山岩以熔岩为主,其岩石化学、微量元素及稀土元素特征表明属大陆拉斑玄武岩,形成于大陆裂谷,该裂谷可能是熊耳期大陆裂谷的延续。     

北秦岭基底杂岩中变质基性岩的性质及其构造背景研究

通过对北秦岭造山带变质基底杂岩中变质基性岩的野外地质调查和岩石地球化学特征的研究，表明秦岭岩群中的变质基性岩应为古元古代晚期侵位的基性岩墙，其化学成分相当于大陆裂谷或板内拉斑玄武岩，代表了吕梁事件的产物，形成于元古宙大陆地壳拉张构造背景的早期阶段，是秦岭造山带中元古代大陆裂谷小洋盆并存构造体制演化阶段的早期地质记录。     

大别山宿松变质带花岗片麻岩的锆石U-Pb年龄和Hf同位素成分

宿松变质带位于大别碰撞造山带南部,是一个相对低级变质的构造岩石单位。该带岩石类型丰富,如云母石英片岩、花岗片麻岩、变玄武岩/斜长角闪岩、变质辉长岩、异剥钙榴岩、大理岩、石墨片岩和含磷岩系等。然而,它们的形成时代和岩石成因一直存在较大争议。为此,重点对大别山宿松变质带中花岗片麻岩进行了锆石SHRIMP U-Pb定年及Hf同位素分析。锆石定年结果表明,这些花岗片麻岩的原岩形成时代包括晚太古代(2.5~2.7Ga)和新元古代(770~830 Ma)两大类,经历了晚三叠纪的绿帘角闪岩相变质作用。新元古代花岗片麻岩的原岩是由经历了约2.0Ga变质作用的晚太古代岩石在新元古代大陆裂解过程中发生重熔作用形成的。鉴于花岗片麻岩的新元古代岩浆锆石年龄记录与大别造山带超高压正变质岩的原岩形成时代一致,结合变质作用特点和已有资料与区域地质背景,进一步证明宿松变质带花岗片麻岩等参与了扬子板块的三叠纪俯冲,并发生了绿帘角闪岩相变质作用,局部可能达到高压榴辉岩相变质作用,是扬子俯冲板块在较浅深度折返的岩片。由于大陆碰撞→造山后的逆冲、推覆以及构造堆叠与剥蚀作用,造成宿松变质带中有可能卷入较深俯冲的岩片。     

通过南海北部陆缘新生代火山岩对南海张开机制约束的研究展望

南海是西太平洋最大的边缘海,其形成演化至今备受争议,其动力演化机制对恢复大陆东南部板块格局和古地理演化等方面有重要作用。南海扩张前后的火山作用形成的火山岩恰可以成为研究南海张开机制的有力证据。而南海海底岩石样品难以获取,于是,一些学者将目光投向了对南海北部陆缘的新生代火山岩的研究,通过研究火山岩成因与深部动力学的联系,从而对南海张开时间进行约束,并探讨其形成机制。     

新疆卡拉麦里姜巴斯套组火山岩地球化学特征与构造意义

通过对新疆卡拉麦里姜巴斯套组火山岩野外地质特征、岩石学和高精度同位素年代学的研究,发现姜巴斯套组火山岩具典型双峰式组合,岩石类型包括玄武岩-酸性火山碎屑岩-玄武粗面安山岩;得到玄武粗面安山岩LA-ICP-MS锆石U-Pb年龄为(319.8±2)Ma(加权均方偏差值为3),表明姜巴斯套组火山岩形成于早石炭世谢尔普霍夫阶。对火山岩地球化学特征的研究表明,姜巴斯套组火山岩钙碱性系列、高钾钙碱性系列和钾玄岩系列岩石兼而有之,岩石的稀土元素配分曲线均为轻稀土元素富集型,无明显Eu异常,玄武岩和玄武粗面安山岩具有K正异常和Sr负异常,酸性火山碎屑岩表现出Nb、Ta和Ti显著亏损。总体来说,姜巴斯套组火山岩富集大离子亲石元素,相对亏损高场强元素。玄武岩和玄武粗面安山岩表现出大陆裂谷(大陆板内拉张区域)岩石特征;酸性火山碎屑岩表现出岛弧或者活动大陆边缘岩石属性。总之,姜巴斯套组火山岩形成于卡拉麦里洋盆闭合碰撞造山后的拉张伸展环境,卡拉麦里地区在早石炭世末期就进入了碰撞后的陆内伸展拉伸阶段。     

西秦岭大水金矿岩浆岩年代学、地球化学特征

西秦岭大水金矿床与其周围伴生的中酸性小岩体的成因关系,直接影响矿床成因的划分和深部资源的开发。中酸性岩浆岩的成因、源区性质及岩体规模对金矿成矿有重要影响。大水金矿岩浆岩地球化学研究结果显示:岩浆系列属于高钾钙碱性系列;岩体球粒陨石标准化稀土元素配分模式具有轻稀土元素富集、重稀土元素亏损、Eu正异常的特征;岩体洋中脊花岗岩标准化微量元素蛛网图显示其富集大离子亲石元素K、Rb、Ba、Th等,亏损高场强元素Nb、Ta、Hf、Zr、Sm、Y、Yb等,花岗岩的w(Sr)-w(Yb)分类属于高Sr、低Yb"C"型埃达克岩。LA-ICP-MS锆石U-Pb法测年获得大水金矿格尔括合岩体和竖井941岩脉的锆石U-Pb年龄分别为(215.8±1.3)、(202.9±1.5)Ma;成矿热液蚀变叠加在脉岩之上,成矿年龄应晚于202.9 Ma的脉岩年龄。Sr-Nd同位素组成具有高初始N(87Sr)/N(86Sr)值、低εNd的特点,模式年龄为1.29~1.47Ga。εSr(t)-εNd(t)图解表明岩浆源区为下地壳;εNd(t)-初始N(87Sr)/N(86Sr)图解暗示西秦岭存在统一的岩浆源区。因此,西秦岭大水金矿在成因上与高Sr、低Yb"C"型埃达克岩密切相关。     

东昆仑得尔龙地区华力西期花岗岩地质地球化学特征及构造环境分析

东昆仑得尔龙地区花岗岩体侵位于二叠纪—三叠纪早期,岩石类型为黑云母花岗闪长岩、黑云母二长花岗岩、二云母二长花岗岩。早期次的黑云母花岗闪长岩中含有暗色的镁铁质矿物包体。SiO2含量为65.04%~73.47%,全碱含量为5.29%~8.52%,K2O/Na2O平均值为0.70,Al2O3平均为14.79%;亏损高场强元素Ta,Nb;∑REE平均为142.9×10-6,轻稀土元素相对富集,(La/Yb)N平均为17.15,δEu平均为0.71,表现为弱亏损。研究表明得尔龙地区花岗岩属次铝-过铝(高钾)钙碱性S型花岗岩,形成于后造山环境;岩浆源区的物质是多源的,主要为地壳物质的重熔,其次为幔源岩浆的底侵。     

Zircon U-Pb geochronology and geochemistry of syenogranites in western Niubiziliang,northwestern Qaidam,Qinghai

The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of a syenogranite located in the western Niubiziliang area,China with the aim of determining its formation time,petrogenesis and the regional tectonic setting. Zircons within the syenogranite are euhedral-subhedral and display rhythmic growth zoning,indicating a magmatic origin. Zircon U-Pb data obtained by LA-ICP-MS indicate the syenogranite formed in the Late Permian (260.7±1.5 Ma). The w(SiO_2) of syenogranites is 70.82%--73.59%,w(Al_2O_3) is 13.49%--14.82%,and w(Na_2O + K_2O) is 7.85%--8.52%,and yield K_2O/Na_2O ratios of 1.06--1.26. Therefore,the syenogranites belong to the high-K calc-alkaline and metaluminous (A/CNK 1,A/NK 1) series which display I-type granites similarly. The syenogranites also show the geochemical characteristics of volcanic arc rocks,being enriched in large-ion lithophile elements (LILEs; K,Rb) and light rare-earth elements (LREEs; La,Ce,Sm,Nd),but depleted in high field strength elements( HFSEs; Ta,Nb,P,Ti). On the whole,trace element ratios are close to the mean of the Earth's crust,indicating a lowercrust magma source. The low Sr (161--214) ×10~(-6) and Yb (1.08--1.80)×10~(-6) concentrations indicate that plagioclase and hornblende are residual mineral phases in the source. The regional geology and whole-rock geochemistry suggest that the formation of the syenogranites was related to subduction of the Zongwulong Ocean crust,and the north margin of Qaidam Block during the Late Permian was in an active continental margin tectonic setting.     

Petrogenesis of Early Cretaceous riebeckite granophyres in southern Da Hinggan Mts.

This paper reports lithologic features,K--Ar age and geochemical data of riebeckite granophyres from Aliwula area in the southern Da Hinggan Mts.,aiming to reveal the petrogenesis of riebeckite granophyres.K-Ar age of riebeckite granophyres is 126 ± 2 Ma,implying that the riebeckite granophyres formed in the Early Cretaceous.The granophyres are rich in riebeckites and with a lot of melt-fluid inclusion in its quartz phenocrysts.The granophyres are characterized by extensive enrichment in SiO2,FeO,and(Na2O+K2O) and depletion in MgO and CaO,strong negative Eu anomalies and strong positive Ce anomalies.Additionally,the riebeckite granophyres not only have high total REE contents and display enrichment of HFSEs(for example Zr,Hf,Nb,Ta),but also are strong in depletion of LILEs(e.g.Ba,Sr) as well as high Ga /Al ratios.Primitive mantle-normalized REE pattern significantly displays REE M--W tetrad effect.REEs fractionate evidently and highly enrich in LREE,but are uneven distribution in the rocks.Taken together,we conclude that the riebeckite granophyres are similar to typical A-type granite,which could be derived from stretching environments in the Early Cretaceous.The granophyres originated from residual melt which underwent highly differentiation process,and were formed in magmatic-hydrothemal transition stage at last.     

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.     

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。     

Distribution and characteristics of volcanic reservoirs in China

About forty productive oil/gas fields hosted in volcanic reservoirs have been found since 1957 in fourteen basins of China. They can be simply subdivided into two groups, the east and the west. Reservoir volcanic rocks of the east group are predominantly composed of Late Jurassic to Early Cretaceous rhyolite and Tertiary basalt, preferred being considered as rift type volcanics developed in the circum-Pacific tectonic regime. Those of the west are Permo-Carboniferous intermediate/basic volcanic rocks, being island-arc type ones developed in paleo-Asian Ocean tectonic regime.     

Geochronology,geochemistry and geological significance of Early Cretaceous volcanic rocks from Niangniangshan Formation,Ningwu Basin,middle and lower reaches of the Yangtze River

Ningwu Basin is one of the Mesozoic continental volcanic basins in the middle and lower reaches of the Yangtze River.The volcanic rocks of the Longwangshan,dawangshan,Gushan and Niangniangshan formations,as well as the homologous subvolcanic rocks or small intrusions,are developed from old to new in the Ningwu Basin.Zircon U-Pb dating results show the latialite phonolite of Niangniangshan Formation was erupted at 128±1 Ma(i.e.,Early Cretaceous).The latialite phonolite contains moderate SiO2 contents(57.28%-60.96%)with high Na 2O+K 2O contents,belonging to shoshonite series.The samples have high REE contents,and display right-inclined REE distribution pattern.They are characterized by enrichment in some large ion lithophile elements(e.g.,LILEs,Rb,K),and depletion in some high field strength elements(e.g.,HFSEs,Nb,Ta,Ti).All volcanic samples have relatively depleted Nd isotopic compositions(ISr=0.707197--0.707878;εNd(t)=-0.5--0.9),indicating no genetic relationship with the lower crust of Yangtze plate,but a drift trend towards the EMII.The geochemical data suggest that the Early Cretaceous latialite phonolite was derived from the partial melting of an enriched lithospheric mantle metasomatized by subduction-related fluids in an arc-related setting.Based on the temporal and spatial distribution and geochemical variation characteristics of the regional volcanic rocks,it is suggested that the tectonic system within the study area changed from a subduction-related compression to an extensional environment in the early Early Cretaceous,which was caused by the ridge subduction of the Paleo-Pacific Ocean.     

Rare earth elements in sediments of the China continental shelf

Determination of the concentrations of, 15 rare earth elements (REE) in China continental shelf sediments by X-ray fluorescent spectral analysis of selected representative sediment samples showed that REE concentration in the sediments is 156 ppm, similar to that in China loess and Fujian granite, but different from that in Pacific sediments. The shelf REE have the characteristic distribution pattern of typical continental crust REE and evidently philo-continental property. The above findings suggest that weathered materials transported from the China continent are the main source of the REE in China continental shelf sediments. Experiments show that REE exist mainly in the crystal lattices of clay minerals (<2μ) as isomorphs and that REE have close relation with most elements (Al, Ti, K, Rb, Fe, etc.) related with clay minerals, but have negative correlation with the biophile elements Ca and Sr. Contribution No. 1520 from the Institute of Oceanology, Academia Sinica.     

翁泉沟硼铁矿床地质特征

翁泉沟硼铁矿床赋存于早元古宙辽河群里尔峪组。原岩为一套在裂谷环境下形成的中酸性火山岩及碳酸盐岩。矿体的容矿岩石是镁质大理岩。矿体厚度与容矿岩石厚度呈正相关关系。矿石矿物有硼镁石、硼镁铁矿、遂安石等,伴生矿物达64种。根据矿石所含的矿物种类,翁泉沟硼铁矿床矿石类型可分为磁铁矿型、硼镁石型、硼镁石—磁铁矿型、含硼镁铁矿—硼镁石—磁铁矿型等4种类型。硼镁铁矿是在火山喷气和深海沉积作用下形成的层控火山沉积变质矿床。