广西海洋山花岗岩基特征及其含矿性

广西海洋山化岗岩基侵位于海洋山复式背斜核部,形成于晚志留世。岩基划分为４个单元,归并为１个超单元,建立了海洋山花岗岩普系单位。岩石学、岩石化学,微量元素及稀土元素化学特征表明,海洋山超单元各单元为壳源重熔型花岗岩浆不断分异演化的产物。花岗岩基为一大型复合式矿岩体,与Ｗ、Ｓｎ、Ｓｂ、Ｐｂ、Ｚｎ等矿化有的关系。     

南岭中生代姑婆山-花山花岗岩基及其热接触变质围岩的应变特征和应变分析

采用Rf /φ法对姑婆山-花山花岗岩基及其热接触变质围岩进行了系统的应变测量,共测量了153个三维有限应变测量点、1.5万余个应变标志体。结果表明：（1）姑婆山-花山花岗岩基热接触变质围岩和早期侵位的牛庙、杨梅山独立侵入体及里松和望高单元以压扁型应变为主,晚期侵位的新路单元则为拉长型应变。（2）姑婆山-花山花岗岩基的平均应变强度和平均压缩率均小于热接触变质围岩的平均应变强度和平均压缩率,且岩基内从早期单元到晚期单元（除新路单元外）平均应变强度和平均压缩率均逐渐减小;热接触变质围岩内应变强度和压缩率向岩基接触面方向递增,存在较明显的应变强度梯度和压缩率梯度。另外岩基南侧以碳酸盐岩为主的热接触变质围岩的压缩率远高于北侧以碎屑岩为主的围岩压缩率。（3）姑婆山-花山花岗岩基应变型式表现为近接触变质围岩及各花岗岩单元边部的应变椭圆长轴多与接触界线相协调,最小主应变轴与接触界线多呈大角度相交;各单元中部的应变椭圆展布则比较凌乱、定向性不明显。上述特征表明,姑婆山-花山花岗岩浆的多期脉动侵位在岩体及其围岩内产生较强的应变叠加,而岩浆内部的主动侵位动力应是造成岩体及其热接触变质围岩变形的主要动力,且在岩浆多次脉动侵位过程中,岩体内早期单元及其围岩主要遭受的是径向挤压作用。     

花岗岩区单元-超单元-岩基段填图方法概述

近几年英、美等国加强对花岗岩地区的区域地质研究工作,采用了近似于对沉积岩区的填图方法。具有代表性的,是对秘鲁海岸花岗岩岩基填图中创立的单元-超单元-岩基段填图方法。该方法的理论基础是:花岗岩岩基是复式岩体;花岗岩岩基是多幕深成活动造成的;侵入体的成分和结构的分带,常是多次岩浆活动的产物。在填图中要解决的关键是:查明花岗岩岩基和岩体的内部结构;查明花岗岩的侵位序次;建立起不同等级的构造单元或填图单位;寻找岩基的典型地段和典型剖面。我国已在江西等省开始进行这种花岗岩地区新填图方法的实践工作。     

念青唐古拉花岗岩的同位素年龄测定及其地质意义

念青唐古拉花岗岩体位于西藏当雄县境内,是拉萨地块中部出露的巨型侵入岩岩基,其面积超过1500km2,以大面积出露的黑云母二长花岗岩为主体。本文分别应用单矿物K-Ar法、全岩-单矿物Rb-Sr等时线法和高灵敏度高分辨率离子探针法(SHRIMP-)对念青唐古拉岩体不同位置上的代表性岩石样品进行同位素测年,得到中细粒黑云母二长花岗岩的K-Ar年龄为8.49±0.14Ma,Rb-Sr等时线年龄为8.07±0.35Ma和8.70±1.40Ma,SHRIMPU-Pb年龄为18.3±0.4Ma;中粗粒黑云母二长花岗岩的K-Ar年龄为9.80±0.35Ma,Rb-Sr等时线年龄为9.33±0.41Ma,SHRIMPU-Pb年龄为11.01±0.24Ma。不同方法测年结果均表明念青唐古拉花岗岩形成于中新世,属拉萨地块内部最年轻的巨型花岗岩岩基,其侵位结晶时代处于青藏高原地壳由南北向挤压增厚向东西向伸展的转变时期,岩浆来源于地壳局部熔融,属后碰撞构造-岩浆活动的产物。     

崔召花岗岩岩体的磁组构特征及其构造侵位意义

侵入岩体的磁组构形成于岩浆运移侵位、固化的过程中,必然保留了岩体的构造侵位过程的信息.以玲珑复式花岗岩岩基南部的崔召岩体为例,对岩体磁组构的详细研究,可以揭示岩浆运移,就位和变形等一系列特征.崔召岩体的磁线理不发育,反映岩体侵位速度慢,岩体边部磁面理比内部发育,并且岩体边缘磁各向异性度P值明显大于岩体内部,磁线理倾角小,反映岩体侵位过程中侧向挤压作用比较强烈,具有类似于气球膨胀作用的侵位机制.并且此磁组构特征再没有受到后期构造热事件的影响.     

藏南冈底斯岩基花岗岩锆石U-Pb年龄、Hf同位素特征及其地质意义

冈底斯岩基位于西藏南部拉萨地块的南缘,雅鲁藏布江缝合带北侧.冈底斯岩基向西延伸与科希斯坦-拉达克岩基相连,向东延伸为察隅-滇西-缅甸岩基,整体延伸达3000 km以上.该岩基的主要岩石组合包括钾长花岗岩、二长花岗岩、花岗闪长岩、闪长岩和辉长岩等.     

罗霄山脉中段志留纪花岗岩岩石谱系单位特征及侵位机制探讨

罗霄山脉中段出露有黄洋界、汤湖两处花岗岩岩基和同时期侵位的岩株、岩瘤，其成岩时代属志留纪，按其侵位构造、岩石组合、地球化学等特征，可建立5个岩石单元，归并为汤湖超单元。岩浆的侵位受区域性大断裂左旋剪切应力控制，空间上呈现由南东往北西逐渐变新的特点。     

一个多重的复式岩基

海岸岩基是一个巨大的多重复式侵入岩体,主要由英云闪长岩和花岗闪长岩组成,占据了西科迪勒拉长1600多公里的核心地域。尽管出现了大量独立的侵入体,且岩性范围变化较大,但在整个岩基中,其侵位机制具有一致的简单形式,其组成岩石可分成为数不多自然成分单元。这些单元明显代表具有时间间隔的多次脉动岩浆侵入。在上升和定位之时,每一次侵入的熔体演化成分经典的、同源的由基性到酸性岩套。     

优地槽区花岗岩单元－超单元填图效果初探

以１：５万茶洛、阿冬纳幅为实例，介绍了优地糟区花岗岩单元。超单元填图工作概况。详细论述了解体岩基的方法及不同先后侵位的岩石单元的差异性在单元－超单元划分的可信度研究中论述了划分、归并的依据，并从大量的测试数据及其演化规律中印证了宏观上解体的正确性。作者认为在优地槽区也同样能开展花岗岩单元－超单元填图工作。     

西藏拉萨地块盐湖复式岩基中花岗斑岩的成因及其对班-怒洋闭合时限的制约

花岗质岩浆作用是大陆地壳演化、爆发式火山活动、稀有金属成矿等的关键过程。位于拉萨地块北部班公湖-怒江缝合带西段的盐湖复式岩基,是班公湖-怒江特提斯洋俯冲消减岩浆响应的重要组成部分。以西藏革吉县盐湖复式岩基中的花岗斑岩为研究对象,对其进行岩相学、锆石U-Pb年龄及岩石地球化学研究,探讨其成因。研究结果表明,盐湖复式岩基花岗斑岩的锆石U-Pb年龄为103.8±0.8 Ma(MSWD=3.0,n=25),侵位于早白垩世晚期。盐湖复式岩基花岗斑岩铝饱和指数(A/CNK)为1.05～1.08,显示弱过铝质特征,具有高K₂O、Na₂O含量,低Mg^#值(12.43～22.36)的特征,为高钾钙碱性I型花岗岩。盐湖复式岩基花岗斑岩富集K,亏损Ba、Nb、P、Zr、Ti,具有强的负Eu异常(δEu=0.20～0.48),稀土元素配分曲线呈轻稀土元素较陡、重稀土元素较平坦的右倾型,ΣREE=81.33×10^-6～121.61×10^-6,LREE/HREE=5.75～6.74,具有较高的Y(20.1...     

Geochemistry, geochronology and mineralisation potential of the granites in the Central Iberian Zone: The Jalama batholith

The Jalama batholith (Spain and Portugal) is one of the numerous granites of the Central Iberian Zone with Sn- and W-associated mineralisation. On the basis of petrographical and geochemical characterisation three types of granite have been distinguished: inhomogeneous granitoids, porphyrytic granites and leucogranites, all of these being peraluminous and subalkaline. All the granites correspond to S-type granites. The field data, the petrography and lack of geochemical affinity relationships of the leucogranites with the remaining granites indicate that their geneses correspond to an independent magma batch and superimposed fractional crystallisation process. The granitic units show subparallel REE patterns. There is a decrease in total REE and an increase in the negative Eu anomaly from the inhomogeneous granitoids to leucogranites. Some leucogranites show relatively low contents of Sn and W almost certainly due to segregation in the magma of a melt rich in water carrying Sn-W. These elements are concentrated in the water phase, which eventually gives rise to Sn-W-associated mineralisation.The ages obtained by means of a whole-rock Rb-Sr isochron for the granites mainly indicate an early intrusion of the inhomogeneous granitoids (319±10 Ma), followed in time by porphyrytic granites (279±9 Ma), which can be associated to the late-post-kinematic granites within the third Variscan deformation phase (D₃).Apart from the average Sn content, the variations of trace elements, principally Sr, Ba, Rb, Th and P, establish that the porphyritic granites and the inhomogeneous granitoids will be barren granites while the leucogranites and the subfacies at the margin of the porphyritic granites correspond to granites with mineralisation potential. It is precisely in these granites of the Jálama batholith that the Sn-W mineralisation is located, for which the criteria utilised has been demonstrated to be effective.     

南岭成矿带中—晚侏罗世成钨、成锡、成铅锌（铜）花岗岩的差异性研究

【研究目的】南岭地区以发育强烈的中—晚侏罗世岩浆作用与相关金属成矿作用为主要特色,这些金属矿床尤以钨、锡、铅锌铜最具代表性。对这3类成矿花岗岩开展系统的对比研究,深入分析成矿差异原因,对指导区域找矿具有重要意义。【研究方法】本文通过搜集已发表的主量元素、微量元素、年代学、Sr-Nd-Hf同位素和矿物化学数据,并结合项目组长期野外地质调查进展,对3类成矿花岗岩进行了差异性研究。【研究结果】通过对比发现成钨、成锡、成铅锌铜3类花岗岩在时空分布格局、野外地质特征、矿物组成、源区性质、包体成因类型、岩浆分异程度、形成温度和氧逸度等方面具有明显的差异。【结论】笔者认为花岗岩的岩石地球化学成分、源区物质组成、岩浆分异程度以及岩浆演化过程中物化条件(如氧逸度)的综合差异是导致南岭花岗岩形成3类不同金属矿床的主要原因。在此基础上,进一步完善了南岭成矿带成钨、成锡、成铅锌铜花岗岩的综合判别标志,指导区域找矿勘查。     

The Ackley City Batholith,southeastern Newfoundland: Evidence for crystal versus liquid-state fractionation

The 345 ± 10 Ma old composite Ackley City Batholith of southeastern Newfoundland, consists largely of very felsic K-feldspar megacrystic granite and alaskite. Spatially related to the southeast contact of the alaskite are younger aplites and pegmatite, intrusive phases which are interpreted to be pan of a tilted, high level roof zone complex to the batholith. The compositions of the alaskite and roof zone complex define major and trace element gradients similar to those in voluminous high-silica eruptive suites; i.e., the alaskite is more chemically evolved (higher in Rb, lower in Ca, Fe, Mn, Ti, P, Sr, Ba and LREE) toward the roof. Apparently these chemical gradients in the batholith are restricted to the top 2 to 3 kms of the former magma chamber. Fractional crystallization is a plausible process for generating the chemical dispersion in the granites, although very high feldspar partition coefficients for Ba, Sr and Eu are required to generate the observed chemical gradients by a reasonable degree of fractional crystallization. Restriction of crystal fractionation to near the roof of the batholith may reflect a decreased viscosity which would facilitate crystal-liquid separation by processes such as filter pressing, flow differentiation or convective fractionation.The chemical gradients in these granites closely resemble those attributed in high-silica volcanics to the process of thermogravitational diffusion (TGD). Compositional gradients in the upper portion of a magma chamber are consistent with the TGD model. This model, although still poorly understood, is, like fractional crystallization, a plausible mechanism to generate the chemical features of the Ackley City granites.     

皖南绩溪伏岭岩体岩石地球化学特征

通过详细的野外填图和地球化学研究，发现皖南伏岭岩体具有高硅、富铝、富碱，富集高场强元素，富集REE，高Rb、低Sr、Ba的特点，属于铝质A型花岗岩。地球化学特点表明岩浆由下地壳部分熔融产生；岩体是在造山后伸展构造环境中沿断裂快速上升定位、分异作用不完全状态下形成。     

大兴安岭南段维拉斯托高分异花岗岩体的成因与演化及其对Sn-(Li-Rb-Nb-Ta)多金属成矿作用的制约

近年来,大兴安岭南段维拉斯托矿区深部Sn-Li找矿取得重大突破,但人们目前对与成矿作用密切相关的深部花岗岩体成因与演化及其对稀有金属矿化存在怎样的制约尚不清楚.为此,针对该岩体开展了年代学、地球化学和Sr-Nd-Hf同位素组成研究,获得的锆石LA-ICP-MS U-Pb年龄为130.7±0.5 Ma（MSWD=0.53）,属早白垩世岩浆活动产物.化学组成上表现为高硅、富碱（高钠）,贫钙、镁、铁和极低P₂O₅（< 0.01%）含量特征,铝饱和指数（A/CNK）集中于1.02~1.08,全岩Rb/Sr、Nb/Ta比值高,Zr/Hf比值低（< 4）.岩体富Cs、Rb、Th、U、Nb、Ta以及Li、F等元素,亏损Ba、Sr、Ti和稀土元素,轻重稀土比值小,并具显著的四分组效应和Eu负异常（δEu=0.02~0.15）,锆石饱和温度（691~727℃）和Zr+Nb+Ce+Y含量均低于A型花岗岩,以上综合特征反映其应属准铝-弱过铝质高分异I型花岗岩类.岩体具正的ε_Nd（t）（+1.10~+3.75）值和相对均一的ε_Hf（t）（+4.2~+8.7）以及年轻的二阶段模式年龄（T_（Nd）DMC=607~829 Ma;T_（Hf）DMC=627~914 Ma）,说明成矿岩体的岩浆源区可能来自于含大量幔源组分新生下地壳的部分熔融.Sn-（稀有）成矿受岩浆后期的高度分异演化和晚期流体-熔体相互作用共同影响,并与外围的脉状矿体共同构成岩浆-热液成矿系统.      

Post-subdution evolution of the Northern Lhasa Terrane,Tibet: Constraints from geochemical anomalies,chronology and petrogeochemistry

Bangong-Nujiang collisional zone(BNCZ)is an older one in Qinghai-Tibet Plateau and resulted in the famous Bangong-Nujiang metallogenic belt,which plays an important role in evaluating the formation and uplift mechanism of plateau.The northern and central Lhasa Terrane composed the southern part of the BNCZ.Since ore deposits can be used as markers of geodynamic evolution,the authors carried 1∶50000 stream sedimental geochemical exploration in the Xiongmei area in the Northern Lhasa Terrane to manifest the mineralization,and based on this mineralization with geochemical and chronological characteristics of related magmatic rocks to constrain their geodynamics and connection with the evolution of the Lhasa Terrane.The authors find Early Cretaceous magma mainly resulted in Cu,Mo mineralization,Late Cretaceous magma mainly resulted in Cu,Mo,and W mineralization in the studying area.The results suggest a southward subduction,slab rolling back and break-off,and thickened lithosphere delamination successively occurred within the Northern Lhasa Terrane.     

斑岩型铜、金、钼矿床成岩成矿特征差异的原因和意义

文中简要总结了斑岩型金矿、铜矿和钼矿在产出的构造环境,岩石地球化学特征和出溶流体的温度、压力、盐度、蚀变等方面的异同点,重点从元素的地球化学性质、岩浆的源区和过程(熔体和流体演化)3个方面解释了上述差异。Au、Cu和Mo在地球化学性质尤其是亲硫性上的差异决定了元素在不同的大地构造环境下的岩浆作用过程中的分布、迁移和富集特征,最终控制了矿床的分布。岩浆的源区及其温压条件、熔体上升过程中矿物的分离结晶和中上地壳岩浆房内的演化程度控制了成矿岩浆的地球化学特征,进而影响其就位时的压力和温度,从而导致出溶流体在p-T-X上的变化。结合岩浆岩中大离子亲石元素和SiO2的含量,可以评估斑岩型矿床的类型：高的Rb含量是斑岩型钼矿的特征,高的Ba含量是斑岩型钼+铜矿的特征,高的Sr含量是斑岩型铜+金矿的特征。相对于俯冲环境,后俯冲环境下的成矿岩体具有更高的大离子亲石元素含量。矿区中酸性岩石的结构(斑状、似斑状、不等粒和等粒结构)可以用来初步指示成矿的潜力。     

从云母微量元素特征探讨华南花岗岩的成因和演化

云母中微量元素可分为浅源指示元素和深源指示元素。浅源指示元素Nb、Ta、Sn、Li、Rb在南岭系列云母中的含量高于长江系列,而深源指示元素Co、Ni的含量长江系列大于南岭系列。云母中Nb、Ta、Sn、Li、Rb变化特征是自身成矿演化的直接示踪剂,而Co、Ni变化特征是Fe、Cu、Au、Mo(W)、Pb、Zn成矿演化的重要示踪剂。云母中Cu、Zn、W、Mo、U、Th等元素呈波动性变化,不能灵敏指示花岗岩的成因与演化。微量元素在云母中的选择分布主要受岩浆物源化学背景的制约,同时也受岩浆侵位和分异演化程度高低以及结晶的物理化学条件变化等因素的影响。     

A flow-foliated ignimbrite related to the Åland rapakivi granite in SW Finland

A flow-foliated felsic ignimbrite constitutes the uppermost lithological unit of the 1.58 Gyr anorogenic magmatic rocks in SW Finland. The ignimbrite is derived from an explosive eruption of hot (≅ 950 °C) phenocryst-bearing A-type (rapakivi-type granite magma.
The ignimbrite is close in composition to subvolcanic rapakivi granites that occur in the margins of the kand rapakivi batholith. The subvolcanic granites crystallized under a pressure of ≅ 1 kbar and at temperatures of about 650–700 °C. However, both major and rare earth elements show that the ignimbrite- forming magma was more fractionated than the magma forming the subvolcanic varieties.
Supported by evidence of mafic-felsic magma mingling, it is suggested that injection of hot mafic magma into a shallow magma chamber produced the high temperature of the ignimbrite-forming magma. This injection increased the magmatic and the volatile pressure that caused the eruption of the dry felsic magma.     

A preliminary discussion on the geochemical role of country-rock media in cassiterite-polymetallic sulphide mineralization,Dachang ore field,Guangxi, China

Our metallogenic studies of the Dachang ore field show that the country-rock media have great influence on the process of mineralization. They can not only contribute part of the ore-forming material, but also have influence on the geochemical evolution of granitic magma and ore fluids. The Dachang ore field can be taken as a typical example to show the influence of country-rock media on mineralization. Geological field investigations indicate that where granites intruded weakly alkalic country rocks (e.g. middle Devonian limestones and silicorites of platform facies in the Dachang), instead of carbonaceous shales of reducing basin facies, Sn would be able to enter rock-forming minerals in large quantities to form cassiterite-sulfide ore deposits of commercial value. So, it may be concluded that the process of magmatic differentiation-evolution, mineralization and tectonic settings of ore deposits are, more or less, controlled by their country-rock media.