太行山东麓构造岩浆带在豫北安林地区的活动特点及控矿特征

安林地区的构造活动,对剖析太行山东麓构造岩浆带成生、演化具有一定的代表性。本区自燕山运动开始就受到了变质核杂岩和伸展拆离构造控制,区内主要构造有NNE向和NW向两组,其中NNE向构造在区内等间距形成了五条规模大的深断裂,均具高角度正断层性质。NW向构造形成了天喜镇-磊口北西向构造岩浆岩带,包括了塔山穹窿式背斜和白玉村-宝山墙状岩体,两组构造均对燕山晚期中-碱性岩浆上侵和安林式矽卡岩型铁矿的形成具重要控制作用。     

浙江中生代陆缘火山岩金矿成矿系统

浙江地处中国东南沿海大陆边缘火山岩成矿带，已发现众多金（银）矿床（点），它们在空间上往往不是孤立地出现，而是在数十至数百平方公里内围绕岩浆热中心相对集中，并与有色金属在矿田范围内伴生。研究证明，金（银）及有色金属矿床是同一火山—侵入旋回过程中形成的有成因联系的矿床。笔者将这种在同一火山—侵入旋回间，围绕同一个岩浆热中心，在不同深度和水平距离内形成的一系列具有成因联系的金（银）和有色金属矿床的总和称为火山岩金矿成矿系统。本文在此概念基础上，详细论述了浙江中生代陆线火山岩金矿成矿系统的类型。时空结构和物质来源。     

Liquidus Equilibria in the System K2O-Na2O-Al2O3-SiO2-F2O-1-H2O to 100 MPa: II. Differentiation Paths of Fluorosilicic Magmas in Hydrous Systems

We investigated phase equilibria in the six-component systemNa₂O–K₂O–Al₂O₃–SiO₂–F₂O_–1–H₂Oat 100 MPa to characterize differentiation paths of naturalfluorine-bearing granitic and rhyolitic magmas. Topaz and cryoliteare stable saturating solid phases in calcium-poor systems.At 100 MPa the maximum solidus depression and fluorine solubilityin evolving silicic melts are controlled by the eutectics haplogranite–cryolite–H₂Oat 640°C and 4 wt % F, and haplogranite–topaz–H₂Oat 640°C and 2 wt % F. Topaz and cryolite form a binaryperalkaline eutectic at 660°C, 100 MPa and fluid saturation.The low-temperature nature of this invariant point causes displacementof multiphase eutectics with quartz and alkali feldspar towardsthe topaz–cryolite join and enables the silicate liquidusand cotectic surfaces to extend to very high fluorine concentrations(more than 30 wt % F) for weakly peraluminous and subaluminouscompositions. The differentiation of fluorine-bearing magmasfollows two distinct paths of fluorine behavior, depending onwhether additional minerals buffer the alkali/alumina ratioin the melt. In systems with micas or aluminosilicates thatbuffer the activity of alumina, magmatic crystallization willreach either topaz or cryolite saturation and the system solidifiesat low fluorine concentration. In leucogranitic suites precipitatingquartz and feldspar only, the liquid line of descent will reachtopaz or cryolite but fluorine will continue to increase untilthe quaternary eutectic with two fluorine-bearing solid phasesis reached at 540°C, 100 MPa and aqueous-fluid saturation.The maximum water solubility in the haplogranitic melts increaseswith the fluorine content and reaches 12· 5 ±0· 5 wt % H₂O at the quartz–cryolite–topazeutectic composition. A continuous transition between hydrousfluorosilicate melts and solute-rich aqueous fluids is not documentedby this study. Our experimental results are applicable to leucocraticfluorosilicic magmas. In multicomponent systems, however, thepresence of calcium may severely limit enrichment of fluorineby crystallization of fluorite. KEY WORDS: granite; rhyolite; topaz; cryolite; magmatic differentiation     

The Upper Crustal Evolution of a Large Silicic Magma Body: Evidence from Crystal-scale Rb Sr Isotopic Heterogeneities in the Fish Canyon Magmatic System, Colorado

Batholith-sized bodies of crystal-rich magmatic ‘mush’are widely inferred to represent the hidden sources of manylarge-volume high-silica rhyolite eruptive units. Occasionallythese mush bodies are ejected along with their trapped interstitialliquid, forming the distinctive crystal-rich ignimbrites knownas ‘monotonous intermediates’. These ignimbritesare notable for their combination of high crystal contents (35–55%),dacitic bulk compositions with interstitial high-silica rhyoliticglass, and general lack of compositional zonation. The 5000km³ Fish Canyon Tuff is an archetypal eruption deposit of thistype, and is the largest known silicic eruption on Earth. Ejectafrom the Fish Canyon magmatic system are notable for the limitedcompositional variation that they define on the basis of whole-rockchemistry, whereas 45 vol. % crystals in a matrix of high-silicarhyolite glass together span a large range of mineral-scaleisotopic variability (microns to millimetres). Rb/Sr isotopicanalyses of single crystals (sanidine, plagioclase, biotite,hornblende, apatite, titanite) and sampling by micromillingof selected zones within glass plus sanidine and plagioclasecrystals document widespread isotopic disequilibrium at manyscales. High and variable ⁸⁷Sr/⁸⁶Sr_i values for euhedral biotitegrains cannot be explained by any model involving closed-systemradiogenic ingrowth, and they are difficult to rationalize unlessmuch of this radiogenic Sr has been introduced at a late stagevia assimilation of local Proterozoic crust. Hornblende is theonly phase that approaches isotopic equilibrium with the surroundingmelt, but the melt (glass) was isotopically heterogeneous atthe millimetre scale, and was therefore apparently contaminatedwith radiogenic Sr shortly prior to eruption. The other mineralphases (plagioclase, sanidine, titanite, and apatite) have significantlylower ⁸⁷Sr/⁸⁶Sr_i values than whole-rock values (as much as –0·0005).Such isotopic disequilibrium implies that feldspars, titaniteand apatite are antecrysts that crystallized from less radiogenicmelt compositions at earlier stages of magma evolution, whereashighly radiogenic biotite xenocrysts and the development ofisotopic heterogeneity in matrix melt glass appear to coincidewith the final stage of the evolution of the Fish Canyon magmabody in the upper crust. Integrated petrographic and geochemicalevidence is consistent with pre-eruptive thermal rejuvenationof a near-solidus mineral assemblage from 720 to 760°C (i.e.partial dissolution of feldspars + quartz while hornblende +titanite + biotite were crystallizing). Assimilation and blendingof phenocrysts, antecrysts and xenocrysts reflects chamber-wide,low Reynolds number convection that occurred within the last10 000 years before eruption. KEY WORDS: Fish Canyon Tuff; Rb–Sr isotopes; microsampling; magmatic processes; crystal mush     

江西德兴斑岩铜矿石英闪长玢岩成因及成矿学意义

为探究石英闪长玢岩成因及幔源基性岩浆对斑岩铜矿的贡献,本文选取德兴矿床石英闪长玢岩开展了锆石U-Pb定年、Hf同位素和全岩地球化学研究。获得石英闪长玢岩LA-ICP-MS锆石U-Pb年龄为169 Ma,与成矿花岗闪长斑岩侵位时间一致,岩体为中侏罗世岩浆活动的产物。石英闪长玢岩具有低的SiO₂(58.41%~63.12%)和K₂O(1.68%~2.94%)含量及A/CNK值(0.85~1.04),富集大离子亲石元素和轻稀土元素,亏损高场强元素Nb、Ta、Ti和重稀土元素,属于钙碱性到高钾钙碱性系列岩石。具有相对亏损的锆石Hf同位素组成,εHf(t)=2.20~7.93(最大值7.93),指示其源区为岩石圈地幔。锆石稀土元素配分模式图显示出明显的正Ce异常,岩浆氧逸度(lg f_O2)为-20.05~-6.66,达到磁铁矿-赤铁矿氧逸度等级,指示石英闪长玢岩结晶自高氧逸度岩浆。全岩地球化学特征显示,德兴石英闪长玢岩与成矿花岗闪长斑岩及其暗色包体符合岩浆混合的演化趋势,说明成矿花岗闪长斑岩可能是中侏罗世幔源基性岩浆和地壳酸性岩浆大规模混合作用的产物,并且石英闪长玢岩代表了岩浆混合过程中的幔源基性端员。结合前人研究成果,认为在中侏罗世伸展构造背景下,软流圈物质上涌导致新元古代受交代的岩石圈地幔部分熔融形成幔源基性岩浆,基性岩浆的底侵作用诱发下地壳物质熔融并与之发生一定程度的岩浆混合作用,形成了花岗闪长斑岩的母岩浆。高氧逸度幔源岩浆的加入可抑制斑岩体系硫化物的过早饱和,同时为德兴矿床注入了成矿所需的部分挥发分和金属元素。     

Coherent Chemical Variation Trends of the 55-25 Ma Magmatic Rocks in SE Tibet:N-S Direction Lithospheric Stretching of Eurasia during Early Stage of India-Eurasia Collision

The progressive indentation of India into Eurasia generated an E–W-trending orthogonal collision belt and a N–S-trending oblique collision belt. Compiling available data reveals that ～70% of the Cenozoic igneous rocks in eastern and southeastern Tibet are concentrated within an ENE-trending, ～550-km long and ～250-km wide magmatic zone(CMZ) that once separated the orthogonal and oblique collision belts. The Latitude 26°N Line is now its southern boundary. The onset timing of magmatism of the CMZ ...     

一个新颖的哲学理论：突现论及其在地质上的应用

突现论是一个崭新的哲学理论,只有100多年的历史,但是,突现论已经崛起为复杂性系统的核心理论,成为近期哲学领域研究的热点之一。突现论认为,世界是由不同层级（或层次）构成的,不同层次按照事物的复杂程度不断提高划分的。世界基本上有三大层次,从低到高为物理、生命和心灵。突现论有4个特征：1,不同层次性质不同,高层次性质来源于低层次;2,突现具有不可预测的新颖性;3,不可还原性;4,高低层次之间存在因果关系。文中简要介绍了突现论的概念并探讨了突现论在变质岩、岩浆岩、矿床学以及地球演化研究中的可能的应用,希望能够对科学研究的进一步发展有利。     

河南方城大庄铌-稀土矿床碱性正长岩成矿机理研究

【研究目的】河南方城大庄是新探明的中型铌-稀土矿床（Nb₂O₃资源量16245 t;伴生TRE₂O₃资源量30147 t）,矿体主要赋存在碱性正长岩内。【研究方法】本文在野外地质调查基础上,对含矿碱性正长岩与无矿碱性正长岩开展了岩石学、岩相学和地球化学的对比研究。【研究结果】研究结果表明,含矿与无矿碱性正长岩均富碱、富铝,为典型的A型花岗岩,两类岩石的碱金属含量无明显差别,但（Na₂O+K₂O）/CaO、FeO^*/MgO、K₂O/MgO等参数明显不同。含矿碱性正长岩高场强元素Nb、Ta、Ce、U、Th、Zr、Y明显富集,Ba、Sr、P、Eu明显亏损;无矿碱性正长岩大离子亲石元素Rb、高场强元素Nb、Ta、Y和Th元素明显富集,而Ba、U、Sr、P、Ti和重稀土元素明显亏损,但亏损程度低于含矿碱性正长岩。【结论】方城大庄含矿碱性正长岩不是无矿碱性正长岩热液蚀变（钠长石化）的结果,二者应是同一岩浆体系不同演化阶段溶体固结的产物,含矿碱性正长岩的分异演化程度明显高于无矿化的碱性正长岩。方城大庄稀有稀土元素的富集与岩浆高演化、分异过程密切相关。这一研究可为区域找矿勘查提供一定的地质依据。创新点：岩石学和地球化学对比研究显示大庄Nb-REE矿中含矿碱性正长岩具有比无矿岩体更高的演化程度,表明成矿元素的富集与岩浆高分异演化密切相关,为找矿勘查提供了一定的岩石学证据。     

湘南香花岭锡铅锌多金属矿田的云母类型及对成矿的指示

湘南癞子岭花岗质复式岩体是香花岭锡铅锌多金属矿田的主要成矿岩体,其中云母广泛出现在各期次岩（矿）体之中。笔者等在对癞子岭岩体岩相学研究的基础上,开展全岩主微量元素地球化学分析,同时对岩浆成因云母（花岗岩中的云母）、热液成因云母（矿化云英岩、晶洞矿物集合体以及条纹岩中的云母）进行了电子探针分析。结果表明,癞子岭岩体为一套高钾钙碱性—钾玄质、准铝质—过铝质花岗岩,癞子岭岩体中的云母主要为铁锂云母,从早期到晚期,呈现出FeO和Al2O3含量降低,K2O、F、MnO和Rb2O含量升高,且Pb、Zn、Fe等成矿元素含量逐渐增加的特征。热液成因云母分为以下两种： ① 产于矿化云英岩和晶洞矿物集合体中的云母主要形成于流体出溶的早期,无围岩组分参与,云母类型由铁锂云母演化为锂云母,主要沉淀Fe、Zn、Pb、Mo等成矿元素;② 产于条纹岩中的云母晚于矿化云英岩和晶洞矿物集合体中的云母,有围岩组分参与,云母类型由黑鳞云母变为富镁黑云母和富铁黑云母再变为金云母,主要沉淀Fe、Sn和W等成矿元素。随着流体演化,云母呈现SiO2、F、K2O含量逐渐降低,MgO含量逐渐升高,相应的成矿元素从富Fe 、Zn、Pb、Mo逐渐过渡到富Fe 、Sn和W。     

中国西北部成矿地质特征及找矿新发现

西北地区地处中亚构造域和特提斯构造域的交汇处,中间夹有塔里木克拉通和华北克拉通的西段。地质历史上,两个克拉通及其裂解的微陆块的形成和运动史,基本约束了中国西北部的构造发展历程。围绕克拉通及微陆块的显生宙造山带基本是其周缘增生的结果,由于大陆运移,其他大陆边缘增生的产物,在早三叠世(210 Ma)大陆汇聚中也添加了进来,这些造山带及其陆块边缘的增生是西北各种内生金属矿床的重要形成背景。同时,新元古代、晚古生代陆内与地幔柱有关的大火成岩省的发育,为铜镍等重要矿床的形成提供了条件。此外,在克拉通及其微陆块形成和后期的叠生盆地中,形成了重要的沉积和沉积变质矿床。西北地区近年来重要找矿发现,不断印证了西北克拉通边缘板块构造增生和板内幔源构造岩浆作用成矿的特点,并对传统的地质背景构造认识提出了挑战。这其中,最具经济价值和地质意义的是3个超大型金属矿床的发现:西天山早石炭世阿吾拉勒火山-次火山岩浆喷溢型磁铁矿矿床、东昆仑早泥盆世夏日哈木岩浆深部熔离-贯入型铜镍矿床和西昆仑侏罗—白垩纪火烧云构造热液型铅锌矿床。阿吾拉勒磁铁矿矿床是中国首例火山-次火山岩浆喷溢型磁铁矿矿床,可与智利的拉科超大型典型磁铁矿矿床对比,且更具有经济价值,该矿床的勘查和研究为深入理解中亚造山带天山及其邻区石炭纪裂谷型火山岩浆作用与成矿提供了研究的范例;夏日哈木铜镍矿是中国近年来最重要的铜镍矿发现,探明镍资源量已达百万吨以上,该矿床的发现为查明中国早古生代末期新的岩浆铜镍成矿事件及其找矿潜力提供了研究新区;火烧云铅锌矿床是新近发现的具有超大型资源潜力的铅锌矿床,也是喀喇昆仑—三江造山带中蕴藏的中新生代巨型铅锌成矿带上最重要的成矿发现,为深化研究青藏高原东北缘巨型铅锌成矿带的成矿物质来源和构造控矿机制提供了新的基地。