热释氡释放过程的实验研究及其结果的讨论

一、前言热释氡,顾名思义,是岩石矿物在加热过程中所释放出来的氡。氡的半衰期为3.825天,放热释氡是指在岩石矿物中处于束缚或封闭条件下与其母体(铀和镭)呈平衡状态的氡。这点已为实验资料所证实。     

广西全州铀矿田流体地球化学及其成矿意义

位于广西全州的铀矿床为中型铀矿床。含矿岩层主要为泥盆系四排组、东岗岭组和榴江组地层。此区域矿床受新宁?资源?灵川(麻城?广济)断裂的分枝及其次级断裂Fl、F3等控制。古花岗岩提供了铀源。在浅部环境下,碳酸根络合物[UO2(CO3)3]4-和[UO2(CO3)2]2-发生分解形成UO22+(也可能与F-结合形成UO2F42-),并最终沉淀形成铀矿床。选取穿插于四排组地层和花岗岩中石英脉或花岗岩样品,对其中的石英进行流体包裹体均一法测温和爆裂法测温。流体包裹体类型为气液包裹体、含子晶包裹体、富气包裹体和CO2包裹体。绝大部分为气液包裹体,均一法实验测得的冰点温度显示盐度较高,平均盐度为10.3%。含子矿物包裹体的存在说明流体的密度和盐度较高。包裹体均一温度差别较大,但整体集中在200℃～280℃,气液包裹体平均均一温度222℃。爆裂法实验测得爆裂温度350℃左右。较高的捕获温度和高的盐度说明成矿流体与岩浆热液密切相关。选取样品进行碳同位素测试,得出碳的来源为岩浆碳,选取样品进行氢氧同位素测试,表明流体来源既有岩浆源,又有与岩浆热液密切相关的大气降水来源。两个矿化点样品含黑钨矿样品和白钨矿指示了钨的矿化,又由于U-W的共生进而指示了铀的矿化。结合野外观察和地球化学样品分析的数据,成矿主要和燕山期岩体有密切的成因联系。     

矿物热释氡找矿在某地含铀砂岩中的试验研究

该文探讨了矿物热释氡的氡来源较多的原因是每(μm)~3次生含铀矿物或眇岩中有数量巨大的——m×10~n(n>4,m、n为自然数)个的铀离子或晶胞。本文并介绍了取自4210砂岩铀矿床的坑道、钻孔及其矿区内的河流、陡壁的271个样品矿物热释氡的特征:热释氡晕范围较矿体宽约几十米,在平面、剖面上都有热释氡晕存在,产状与矿体一致,与地层和冲刷面有一定交角。表明热释氧晕受层位、岩相、构造等多种因素控制。这些特点,对指导技矿和分析矿床成因,无疑是有意义的。     

矿物中群体包裹成分分析方法讨论

目前激光拉曼探针直接测定抛光片中矿物单个包裹体气液相组分,所获得的是分子团相对摩尔分数,而不能获得包裹体中流体的阴、阳离子和成矿元素组分,因此群体包裹成分分析仍然是进行矿床地球化学研究、获得成矿流体有关信息的首选方法。矿物群体包裹体成分分析,除要求榈必须是纯净的单矿物（９９％以上）外,还要了解样品中原生和次生包裹体的含量、特征、大小、气液比以及它们各自的均一温度、爆裂温度和盐度等情况,以便确定样品     

热液金刚石压腔外压对包裹体均一温度的影响

常压下通常用冷热台测定流体包裹体均一温度,然而因内压的存在使得包裹体在加热的过程中为非等容变化,较大的内压甚至可以使流体包裹体在测温过程中发生爆裂。本文利用热液金刚石压腔(HDAC),以水作为传压介质,通过施加一定的外压对利用高压釜合成的不同体系的合成流体包裹体样品和来自玉龙铜矿的H2O-CO_2体系的天然流体包裹体样品进行测温实验,来研究不同外压下的均一温度变化,结果显示随着外压的增大,包裹体均一温度降低,包裹体发生形变,体积变小。     

某些稀有、有色金属矿床及花岗岩中包裹体微量气体色谱分析研究

研究表明:不同成岩成矿作用不但与温度、压力有关,而且微量气体成分及其含量也有明显的规律变化.例如某爆发岩筒中,酸性气体(HCl、HF、H_2S)含量一般高于不活泼气体(N_2等);随着温度的下降,酸性气体含量减少,而后者增加.在某些地区远离花岗岩体矿物包裹体中CO_2含量有规律地增加,对矿物包裹体中微量气体成分及其含量的研究,有助于解决成岩作用机制,成矿阶段划分及矿床成因.同时,对地球化学找矿,隐伏矿体的揭露也有指导意义.包裹体中微量气体的变化可以作为一个地球化学指示剂.我们在自行研制真空爆裂微量气体测量分析仪的基础上,1979年春,首次成功地使用带热解炉的色谱仪测定了矿物包裹体中H_2O和CO_2等微量气体组分.同时对该色谱仪进行了改装,使该仪器更适合于矿物包裹体微量组分的测定及研究.通过近400多个     

阳春锡山钨-锡矿床含矿石英脉包裹体地球化学实验小结

在小南山含钨石英脉型钨矿床石英包裹体地球化学资料的基础上,我们对锡山矿床又做了进一步实验:采集了45个石英和6个花岗岩样品,分别进行了均一温度、包裹体成分(包括液相和气相)的测定。结果表明,矿脉中石英包裹体均一温度底部稍高于浅部,而元素总的变化趋势是矿脉底部低于顶部,尤其是CO_2。这些现象为地球化学找矿提供了重要线索。     

爆裂法实验条件的讨论

近年来,对矿物中气液包裹体(以下称包裹体)爆裂法测温在我国一些单位已陆续使用。现已用这种方法在解决矿物形成温度方面,并依此在探讨矿床的成因和找矿等方面收到一定效果。但由于爆裂法干扰因素较多,有时不易区分,所以有人对爆裂法测温的可靠性持怀疑态度,甚至认为爆裂法不可信。几年来我们对爆裂法实验条件进行了一些实验,得出了一些规律性的认识,现总结成文,也许有助于该法的广泛应用。     

石英流体包裹体的岩相学和热爆参数填图在前河金矿中的应用

文章从石英流体包裹体的研究入手,采用矿物学填图的方法,探讨了流体包裹体的岩相学特征和爆裂温度等热爆参数方面的成因矿物学信息.岩相学填图表明,包裹体大小在8～11μm之间,分布密度越大的样品对应的金矿化越好;依据石英起爆温度、爆裂温度范围、热爆曲线形态及主爆峰值等特点,将矿区所有样品的石英热爆裂归纳为4种基本类型,起爆温度低且具主爆裂峰的Ⅰ型曲线指示有利于金矿化的地段,爆裂峰越高和爆裂温度区间越宽的样品对应的金矿化越好.流体包裹体的爆裂法测温在找矿实践中取得了较好的效果.并通过此方法初步预测了前河金矿区的深部远景.     

江苏主要含矿花岗岩体的地球化学特征及找矿方向

分析了江苏省主要含矿花岗岩体的主元素、微量元素含量,所含黑云母的成分以及包裹体的类型等地球化学特征.结果表明它们大多属于岩浆花岗岩,且以I型花岗岩为主.成矿元素Cu、Pb、Zn在I型含矿花岗岩中普遍有一定程度的富集,其中以Cu的富集程度最好;Cr、Co、Ni在此类岩体中含量亦较高.广泛发育多种包裹体,尤其是发育含子矿物多相包裹体是含矿花岗岩体的重要特征.指出应加强在宁镇中段某些I型花岗岩体中寻找Cu多金属矿的工作.     

Synthetic fluid inclusions - VI. Quantitative evaluation of the decrepitation behaviour of fluid inclusions in quartz at one atmosphere confining pressure

ABSTRACT The decrepitation behaviour of fluid inclusions in quartz at one atmosphere confining pressure has been evaluated using pure H₂O synthetic inclusions formed by healing fractures in natural quartz. Three different modes of non-elastic deformation, referred to as stretching, leakage or partial decrepitation, and total decrepitation have been observed. The internal pressure required to initiate non-elastic deformation is inversely related to inclusion size according to the equation: internal pressure (kbar) = 4.26 D^-0.423 where D is the inclusion diameter in microns. Regularly shaped inclusions require a higher internal pressure to initiate non-elastic deformation than do irregularly shaped inclusions of similar size. Heating inclusions through the α/β quartz inversion results in mechanical instability in the quartz crystal and leads to mass decrepitation of inclusions owing to structural mismatches generated by pressure gradients in the quartz around each inclusion. Long-term heating experiments (∼2 years) suggest that the internal pressure required to initiate non-elastic deformation does not decrease significantly with time and indicates that short-lived thermal fluctuations in natural systems should not alter the inclusion density and homogenization temperature. Inclusions that do exhibit decreased density (higher homogenization temperature) are, however, always accompanied by a change in shape from irregular to that of a negative crystal. Observations of this study are consistent with elasticity theory related to fracture generation and propagation around inclusions in minerals. These results indicate that an inclusion will not be influenced by a neighbouring inclusion, or other defect in the host phase, as long as the distance between the two is >2–4 diameters of the larger of the two inclusions.     

Carbonic fluid inclusions in South Indian granulites: evidence for entrapment during charnockite formation

Field evidence and fluid inclusion studies on South Indian incipient charnockites suggest that charnockite formation occurred during a decompressional brittle regime following the ‘peak’ of metamorphism and regional deformation. The most abundant type of inclusions in quartz and garnet grains in these charnockites contain high-density carbonic fluids, although lower-density fluids occur in younger arrays of inclusions. Discrete fluid inclusion generations optically are observed to decrepitate over well-defined temperature intervals, and quantitative measurements of CO₂ abundance released from these inclusions by stepped thermal decrepitation show up to a four-fold increase (by volume) in the incipient charnockites relative to the adjacent gneisses from which they are derived. Studies based on optical thermometry, visual decrepitation and stepped-heating inclusion release together indicate that entrapment of carbonic fluids coincided with charnockite formation. We confirm that an influx of carbon dioxide-rich fluids is associated with the amphibolite-granulite transition, as recorded by the incipient charnockites, the remnants of which are commonly preserved as the earliest generation of high-density fluid inclusions.     

A Review of Fluid Inclusions in Diagenetic Systems

The study of fluid inclusions can help constrain the conditions at which diagenetic minerals precipitated, leading to a better understanding of the geologic controls and relative timing of changes in porosity and/or mineralising events. Many of the diagenetic minerals are easily deformed and it is important to check for any post-entrapment changes to the inclusions. Possible post-entrapment changes include reaction with the host crystal, necking down, nucleation metastability and thermal re-equilibration. The recommended method of detecting these problems is to examine individual fluid inclusion assemblages (FIAs) and report data for each individual FIA. These studies have been enhanced by the development of new micro-analytical techniques such as micro-fluorescence spectroscopy, micro-infrared spectroscopy, nuclear magnetic resonance, various mass spectrometry techniques and the analysis of individual fluid inclusions using laser ablation/decrepitation methods. Special techniques have been developed for hydrocarbon-bearing inclusions such as the Grains containing Oil Inclusions (GOI), Fluid Inclusion Stratigraphy (FIS), and the Molecular Composition of Inclusions (MCI) techniques. The fluid inclusions that form in some minerals during diagenesis provide the only direct means of examining the fluids present in these systems. They provide useful temperature, pressure, and fluid composition data that cannot be obtained by other means.     

爆裂法作为快速测定流体包裹体中二氧化碳（和其它气体）含量的手段及其在勘探中的使用：以中国山东和河北省金矿为例

The acoustic decrepitation method heats a small monomineralic sample and counts pressure impulses as the inclusions burst when they develop high internal pressures.For aqueous fluids,the decrepitation temperature is correlated with the homogenisation temperature,but gas rich fluids give a distinct and characteristic low temperature decrepitation peak which can be used to recognize gas rich fluid inclusions.This information is useful in exploration for Au deposits,which are frequently associated with CO_2 rich and sometimes CH_4 rich fluids. This distinctive decrepitation occurs because the CO_2 rich inclusion fluids expand according to the gas law and develop internal pressures high enough to burst the host mineral grain at temperatures well below their homogenisation temperatures.In contrast,aqueous fluids condense to a liquid and vapour phase during post-entrapment cooling.Upon subsequent heating their internal pressures do not increase significantly until after homogenisation to a single phase occurs and hence they do not decrepitate"prematurely"as gas rich inclusions do. This behaviour is usually regarded as an annoyance in conventional microthermometric homogenisation studies,but can readily be used as an exploration aid to find mineralisation deposited from such gas rich fluids.Decrepitation results on samples from Cowra Ck, NSW,Australia,which have also been microthermometrically measured for CO_2 content,show that amounts of less than 5 mole % CO_2 are easily distinguished by decrepitation and amounts as low as 1 mole % CO_2 may be determinable. Examples of the use of acoustic decrepitation in the study of 6 gold mines in the Shandong and Hebei provinces of China are discussed.     

Decrepitometry of fluid inclusions in quartz from the guadalcazar granite of Mexico; principles and application to mineral exploration

A simple acoustic decrepitometric method, with which samples of granite quartz are heated to about 600°C while the number of decrepitations are counted, has been developed to study rock samples derived from the mineralized guadalcazar granite in Mexico. Decrepitation temperatures for individual inclusions have also been determined by observing the point at which they rupture upon heating using a microscope heating stage. Decrepitation temperatures of individual fluid inclusions in granite quartz are influenced by a variety of factors notably size, shape, composition, homogenization temperature and proximity to the surface. There is a positive correlation between total decrepitation activity and fluid inclusion abundances (determined optically using point counting methods). Decrepitographs show a period of low intensity decrepitation activity below 390°C followed by a period of intensive decrepitation up to 570°C. The onset of massive decrepitation at around 390°C is constant for all samples, but variations in decrepitation activity often occur between mineralized and barren samples. These variations reflect complex differences in the fluid inclusion populations, but illustrate the potential for applying simple audio-decrepitometry as an aid to mineral exploration in granite terrains.     

流体包裹体爆裂法测温技术可靠性讨论——以江西大吉山钨矿为例

爆裂法是一种经济快速的流体包裹体测温技术,由于该技术的影响因素较多且测试精度往往不是很高,历来受到很多学者的质疑。为了讨论爆裂法测温技术的可靠性,在前人研究的基础上,利用冷热台对大吉山钨矿含矿石英脉中的包裹体爆裂温度进行了显微测温,分析了包裹体个体大小对爆裂温度的影响,发现两者之间存在着明显的反相关性;同时,对数据的进一步分析发现爆裂法测温曲线反映的爆裂峰是2期3类包裹体爆裂叠加的结果,但是实验测得的爆裂温度区间与爆裂法测温结果基本上是吻合的,这说明爆裂法测温技术虽然有较多的影响因素,但是在一定程度上是可靠的,尤其是在找矿勘探方面其潜力很大,值得推广应用。     

山东招远玲珑金矿床含金石英脉石英中流体包裹体特征及成矿温度

本文旨在通过对山东招远玲珑金矿床含金石英脉中流体包裹体特征的观察和测温,对矿床的成矿温度、压力和成矿介质的性质提出一些初浅的看法。     

空气中氡浓度的预测

氡是一种放射性惰性气体,它与肺癌的关系已引起人们的高度重视,世界上许多国家都开展了环境氡的研究工作;氡的母体元素铀、镭在地质环境中的分布与空气中的氡浓度水平有密切关系,通过研究地质环境中铀、镭的分布资料,就能快速定性地评价空气中氡浓度水平.     

γ能谱法测量铀矿石样品镭-氡平衡系数的初步探索

以测定铀矿石镭-氡平衡系数为目的,提出了对铀矿石样本进行γ能谱测量,根据铀系的衰变平衡规律,利用γ能谱中的特征峰计数计算镭、氡含量。推导了镭-氡平衡系数的计算公式,重点对相关参数进行了探讨。该方法简单、快速,进一步完善后可应用于钻孔岩心样本的现场分析。     

拉曼光谱在矿物包裹体成分分析中的应用

拉曼光谱在矿物包裹体成分研究中的应用近年来已有一些报导,而在国内则刚刚开始。 通过矿物包裹体成分的分析可以获得成矿溶液的化学组成及有关的物理化学参数,这是矿床研究的宝贵资料。但是,矿物包裹体极其细小,一般只有几微米到几十微米。样品提取十分困难,且忌污染,分析是超微量的。目前,所采用的破坏性包裹体成分分析方法存在的一些难以克服的缺点影响了分析结果的解释和应用。其缺点是:(1)不能区分原生包裹体和次生包裹体,提供的分析