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。     

论矿物解理、裂隙对爆裂法测温的影响和全岩爆裂曲线的意义

本文从矿物解理、裂隙和矿物包裹体不同的形成机理,及爆裂法测温实践出发,用对比实验探讨了解理、裂隙对爆裂测温结果的影响程度和用全岩代替单矿物测温的可能性,得出矿物的解理、裂隙通常不影响测温结果和全岩可以代替单矿物进行爆裂测温的结论。从而进一步肯定矿物或岩石的爆裂法测温在岩体对比、矿床研究中的实际意义。     

爆裂法测温在矿床地质上的应用

爆裂法是一种快速、经济的获取包裹体有关信息的方法.文章采用爆裂法测温提供的信息,并结合其它研究,综合分析认为新疆北部哈图金矿石英脉型矿体与蚀变岩型矿体成矿流体是不同来源流体叠加成矿,石英脉型与蚀变岩型矿体可以单独成矿;阔尔真阔腊金矿、哈图金矿、康古尔及红石金矿石英爆裂曲线出现强烈的α-β转变峰,其成矿与深部侵入岩浆热液有关,深部可能存在铜金盲矿体;石英滩、野马泉、科克萨依、布尔克斯岱金矿深部成矿可能性不大.实践已经证明上述成矿预测与实际地质找矿勘探结果基本是符合的,证实了爆裂法测温的确能反映重要的成矿信息,在矿床地质及成矿预测研究中可起重要作用.虽然爆裂法测温本身存在的缺陷和诸多不确定因素在一定程度上限制了该方法的进一步发展,但我们的研究实践表明,如果充分利用它的优势,扬长避短,爆裂法具有均一法无法替代的优势.     

江西省全南县大吉山钨矿成矿流体演化特征

大吉山钨矿位于南岭W、Sn成矿省,是我国著名的大型W矿床。本文旨在通过对大吉山脉形钨矿2513号脉中的包裹体进行详细的岩相学及显微测温学研究,对成矿流体的演化过程及矿床形成深度进行探讨。包裹体的岩相学研究表明,包裹体类型复杂主要由富液包裹体、含CO2、CH4三相包裹体及含子矿物包裹体组成;包裹体组合复杂,各种类型的包裹体常叠加在一起;原生、次生包裹体产状区别明显,较易识别,原生包裹体主要由含CO2、CH4三相包裹体及充填度较小的富液包裹体组成,次生包裹体主要为充填度较大的富液包裹体。显微测温分析发现不同类型的包裹体的盐度、均一温度差别显著,呈现复杂的流体演化过程。包裹体的爆裂曲线显示,曲线有高低温两个起爆点,分别对应原次生包裹体包裹体群的起爆温度;由深部到浅部,原生包裹体的起爆温度逐渐降低。利用显微共焦激光拉曼探针仪对原生包裹体进行成分分析发现,成矿流体主要由H2ONaCl和H2OCO2CH4NaCl体系组成。包裹体的显微测温结果显示,成矿流体演化经历了自然冷却、不混溶作用和混合作用等过程,各种过程相互作用造成了钨的沉淀。通过对不混溶包裹体的测温数据进行计算,得出大吉山脉型钨矿成矿流体的压力约为114～132MPa,矿床形成深度约为4.6～5.3km。     

显微红外测温技术及其在金红石矿床中的应用

显微红外测温技术是红外显微镜通过红外成像系统研究不透明和半透明矿物的流体包裹体的丰度和分布特征,并与冷热台相结合,进行流体包裹体显微测温分析的一种技术手段。本文以苏鲁超高压变质带东海榴辉岩中金红石矿床的流体包裹体研究为例,系统介绍了显微红外测温分析技术。结果表明,显微红外测温技术是研究半透明和不透明矿物中流体包裹体的一种十分有效的新手段,可见光和红外光两种光源下流体包裹体的测定不存在系统误差。利用红外显微镜进行半透明-不透明矿石矿物的流体包裹体测定时,循环技术法是测定冰点和均一温度的有效方法。江苏东海地区超高压变质带所经历的早期退变质阶段是金红石矿床的主要形成阶段。显微红外测温技术对研究矿床的成矿流体性质以及矿床成因等具有重要的意义。并将在金属矿床成矿流体的研究领域发挥重要的作用。     

实验室合成石盐包裹体的均一温度以及古气候意义

石盐是表生环境下形成蒸发岩系的主要矿物,在形成过程中捕获大量的原生包裹体。通过低温冷冻测温技术,可以得到石盐中原生包裹体的一系列均一温度,如何正确理解这些数据是应用石盐原生包裹体恢复古气候的关键。石盐沉积可以发生在气水界面以及水体底部,其均一温度记录了卤水结晶的温度。Lowenstein et al. (1998) 曾经用水浴法在恒定水温下合成了人工合成石盐,进行原生包裹体的均一温度研究,然而如何用水温来恢复古气温是古环境解释的关键。本次实验通过40℃下(气温,烘箱中蒸发)人工合成石盐,在岩相学观察基础上,对形成于气水界面漏斗晶中的包裹体和在底水沉积人字晶中的包裹体的均一温度进行低温冷冻测温法测定。测温过程中石盐包裹体可以得到一系列均一温度(10.6~39.9℃),而只有最大均一温度才能反映卤水结晶时的温度,两种类型的包裹体也显示了相似的最大均一温度。因此在浅水环境下,两种包裹体都可以用来反映古气温。     

包裹体爆裂法测试中石英α—β峰的产生原因及找矿意义

石英在爆裂法测试中常出现α－β峰,此峰是由爆裂温度大于５７３℃的高温流体包裹体,在α石英相变成β石英时,包裹体发生泄漏形成的。在金矿地质找矿中,用α－β峰可判断矿脉的剥蚀程度,推测矿床成因。     

石笋包裹体重建古温度的研究进展

洞穴石笋是全球气候变化研究的重要载体,石笋包裹体因其捕获了当时环境条件下的水溶液或气体而封存了古气候的原始信息,因此可以重建古温度。围绕当前石笋包裹体研究的现状,阐述了包裹体的形成机制及其在石笋中的分布特征,讨论了包裹体测温(包括稳定同位素测温法、惰性气体测温法、均一温度测温法)原理、方法和技术,分析了石笋包裹体气候学存在的问题及其发展前景。     

利用过氧化氢法消除矿物连生体

分选萤石作包裹体成分分析和爆裂法测温时,要求粒度0.5到0.25毫米,处理温度不超过50℃。但样品初选后发现萤石与黄铁矿呈连生体。经试验认为选用过氧化氢法为最优方案,效果甚佳,黄铁矿可全部除去。     

包裹体爆裂法测试中石英α-β峰的产生原因及找矿意义

石英在爆裂法测试中常出现α-β峰,此峰是由爆裂温度大于573℃的高温流体包裹体,在α石英相变成β石英时,包裹体发生泄漏（非爆裂）形成的.在金矿地质找矿中,用α-β峰可判断矿脉的剥蚀程度,推测矿床成因     

内蒙古东升庙矿床岩浆热液叠加成矿作用——来自地质与矿物包裹体测温的证据

The Dongshengmiao Pb-Zn deposit located in the Mesoproterozoic aulacogen in a passive continental margin in the north- west margin of the North-China Craton is widely considered to be a untypical SEDEX deposit.Recently,new types of mineralization such as chalcopyrite veins and re-crystallized sphalerite ores with visible hydrothermal alteration have been found in the deposit at depth.In this paper we report the decrepitation temperatures of fluid inclusions in chalcopyrite,sphalerite and quartz from these new types of ores.The decrepitation temperatures of fluid inclusions in chalcopyrite(4 samples),sphalerite(2 samples)and quartz(5 samples)are 303～456℃,97～497℃,146～350℃and 350～556℃,respectively.The decrepitation temperatures of fluid inclusions in the vein-type chalcopyrite are similar to the decrepitation temperatures of fluid inclusions in chalcopyrite from the Hercynian Oubulage porphyry Cu-Au deposit(313～514℃)and the Chehugou porphyry Cu-Mo deposit(277～485℃),supporting our interpretation that the Dongshengmiao deposit was overprinted by magmatic hydrothermal mineralization.The decrepitation temperatures of fluid inclusions in re-crystallized sphalerite from the Dongshengmiao deposit are characterized by two peaks,97～358℃and 358～497℃.The decrepitation temperatures of fluid inclusions in quartz in ehalcopyrite veins from the Dongshengmiao deposit are also characterized by two peaks,146～350℃and 350～556℃.The lower and higher temperature peaks in both cases are considered to represent two separate mineralization events,original SEDEX mineralization and magmatic hydrothermal overprinting,respectively.The higher decrepitation temperatures of fluid inclusions in quartz and sphalerite from the Dongshengmiao deposit are similar to the decrepitation temperatures(340～526℃)of fluid inclusions in sphalerite from the Baiyinnuoer skarn-type Pb-Zn deposit in the region. Replacement of pyrite by sphalerite and overgrowth of chalcopyrite on pyrite in the Dongshengmiao support our interpretation that the original SEDEX mineralization was overprinted by magmatic hydrothermal activity in the deposit.Our results suggest that there may be separate porphyry and skarn-type deposits related to Hercynian magmatism and associated hydrothermal activities in the Langshan area, which are potential exploration targets in the future.     

Near-infrared and Visible Light Microthermometry of Fluid Inclusions in Sphalerite from a Possible Southeast Extension of the Toyoha Polymetallic Deposit, Japan

Abstract. Near-infrared (NIR) and visible light microthermometry was applied to the fluid inclusions in sphalerite from a possible southeast extension of the Toyoha polymetallic deposit. Sphalerite occurs as euhedral-subhedral crystals or collo-form aggregates with a variety of color, which contain a well-developed growth banding. Combined with morphological observations, fluid inclusions in dark-colored sphalerite were examined using a near-infrared light microscopic technique, whereas those in light-colored sphalerite and quartz were examined by a conventional visible light microscopy.
Salinities of fluid inclusions in dark-colored sphalerite have a wide variation (1.0–10.3 wt % NaCl equiv.) compared to that in light-colored sphalerite and quartz (0.0–3.4 wt % NaCl equiv.). These variations suggest that the conventional microthermometric data from light-colored sphalerite and quartz were inadequate to interpret the ore formation process. Dark-colored colloform sphalerite and a dark core of subhedral sphalerite formed from high-salinity fluids (6.5–10.3 wt % NaCl equiv.) under highly supersaturated conditions with respect to sphalerite.
The NIR and visible light microthermometry of fluid inclusions in sphalerite combined with its morphological observations is an invaluable method to infer the formation conditions of sphalerite. The NIR and visible light microthermometry is useful to reveal how the nature of ore fluids changed with time.     

Synthesis of Fluid Inclusion Reference Materials in the H2O–NaCl–CH4 System

In this study, we detail procedures to synthesise inclusions of fluids of known composition under diagenetic conditions – low temperatures (50–180 °C) and pressures (2–25 MPa) – hosted by quartz. Pre‐existing microcavities in polished quartz chips were used, decrepitated and rinsed before being healed in an autoclave. Each synthesis required around 4 weeks. A range of biphase liquid–vapour inclusions in the H₂O–CH₄–NaCl system, similar to natural ones, were synthesised in quartz, varying the content of all three components. The quartz chips were checked before and after synthesis by optical microscopy, microthermometry and Raman spectroscopy. The method was used to build a series of calibration curves relating methane‐to‐water count ratios to the methane content of aqueous fluid inclusions. Good correlation was obtained between Raman band area ratios and the expected CH₄ solubilities from equations of state. The chosen procedure's main advantages, compared with other published methods, are as follows: quicker healing of the microfractures at lower temperatures, larger inclusions, simple quartz sample preparation, control of fluid inclusion composition and the use of commercial reactors. Such reference material inclusions allow the calibration of Raman microspectrometers with the objective of PTX reconstruction of palaeofluid migration in petroleum reservoirs.     

毛细管合成包裹体在激光拉曼探针测定包裹体盐度中的应用

盐度是流体包裹体重要的参数之一,利用激光拉曼探针可以快速、准确地测定包裹体盐度,而标准样品的制备是保证该方法准确性的关键。毛细管合成包裹体技术是一种新型的标准样品制备方法,本文利用该方法,制备了不同组成的H₂O-NaCl样品,并以此建立了测定包裹体盐度的标准曲线。显微测温结果表明,毛细管合成包裹体标准样品盐度的准确性可以达到±0.5%,利用石英和石盐中的合成包裹体对标准曲线进行了检验,结果表明利用标准曲线测定包裹体盐度,测量值与理论值的误差在1%以内。应用该方法制备的标准样品具有操作简便、快捷、样品尺寸与地质样品相类似等特点,兼具了矿物中合成包裹体以及石英试管或玻璃瓶制备标准样品的优势。     

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.     

祁连造山带玉石沟地幔橄榄岩中挥发分的流体化学和稳定同位素组成及古大洋岩石圈演化意义

Fluid inclusions in olivine and orthopyroxene of mantle peridotites from the Yushigou ophiolite can be divided into three types based on decrepitation temperature,shape and distribution.Type-1 fluid inclusions are characterized by oval or negative crystal shapes and small size(<5μm across).They occur in the cores and mantles of the host crystals,and decrepitated at>840℃.Type- 2 fluid inclusions have irregular or tabular shapes with relatively large size(10～100μm in length).They occur in irregular or circular healed micro-fractures in the host crystals,and decrepitated at 612～710℃.Type-3 fluid inclusions have size and shape,similar to type-2 fluid inclusions but occur in micro-fractures restricted to the margins of the host crystals,and decrepitated at much lower temperature from 190℃to 340℃.The three different types of fluid inclusions are interpreted to represent primary,metasomatic (pseudo-secondary)and secondary inclusions,respectively.Stepwise heating reveals three concentration peaks of volatiles at 200～400℃,400～800℃and 800～1200℃released from olivine and orthopyroxene in harzburgite and dunite from the Yushigou ophiolite, which are considered to correspond to the decrepitation of secondary,metasomatic and primary fluid inclusions at similar temperature ranges.CO2 is a major constituent in the volatiles released at three different temperature intervals.Trace amounts of H_2 and N_2 are present in the volatiles released at<800℃and trace amounts of H_2O and SO_2 are mainly present in the volatiles at 400～800℃.TheδD(-95.2‰,-306.3‰)of H_2O and theδ~(13)C(-15.5～-12.5‰)andδ~(18)O values(1.4～1.9‰)of CO_2 released at<800℃are lower than normal mantle values and suggest the mixing origin of crustal fluids( sedimentary organic)with ocean water,implying that Yushigou AOLM had undergone an intensive metasomatism by a fluid composed of CO_2.H_2O and SO_2,and followed by degassing. In contrast,the volatiles released at 800～1200℃are characterized by trace amounts of H_2 and CO in dunite and SO_2 in harzburgite, much lighterδ~(13)C(-29.1‰～-19.5‰),heavierδ~(13)O(8.8‰)of CO_2 and positive relationship between these isotopic ratios and the concentration of CO_2.Such features can be best explained by mixing of significant terrestrial crustal(organic)and minor mantle volatiles.We proposed that the Yishigou peridotites are more likely to have derived from a continental lithosphere instead of an oceanic lithosphere comprising the Yishigou gabbros and pillowed basalts.A supra-subduction tectonic setting is thus inferred for the Yushigou ophiolite.     

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.     

Fluid Geochemistry and Metallogenesis of the Hatu Gold Deposit in the Junggar Basin, Xinjiang

The Hatu large gold deposit is located on the western margin of the Junggar basin, Xinjiang. Its mineralization is characterized by auriferous quartz veins and Au-bearing altered fracturing zones. Studies on mineralogy, inclusions and decrepitation temperature indicate that the gold deposit was formed by overlapping of two kinds of fluid of different origins, instead of gradual evolution of a single fluid. The auriferous quartz veins are related to magmatism-originated fluid, but the Au-bearing altered fracturing zones to deep-derived fluid. Bonanzas in quartz veins were formed and localized at overlapping positions of two types of fluid under intensive compression.     

The use of fluid inclusion decrepitometry to distinguish mineralized and barren quartz veins in the aberfoyle tin-tungsten mine area, Tasmania

In the Aberfoyle Sn/W district of N.E. Tasmania, mineralization is in quartz veins associated with Devonian granite. The host rocks to the mineralization are folded Silurian quartzites, greywackes and shales and these also contain abundant pre-mineralization quartz veins which can be difficult to distinguish from irregularly mineralized ore veins on geological criteria, especially in drill core. It was found that the decrepitation characteristics of the quartz, chiefly the intensity ratio of high and low temperature peaks, which are developed in all decrepigrams, enable a distinction between the two generations of veins to be readily made. The differences between the fluid inclusions in the two generations of veins are relatively subtle, however it seems clear that “CO₂-rich” inclusions having a wide range of composition and density are the main source of decrepitation events and that the major differences in decrepitation behaviour can be correlated with differences in average homogenization temperature of these inclusions. Even those ore veins which have undergone moderate ductile deformation have the typical signature of their origin. The decrepitation results are supported by analyses of inclusion gases by Raman microprobe. These analyses differentiate a third group of veins which are possibly unmineralized veins belonging to a separate hydrothermal system.     

流体包裹体爆裂法在山东焦家金矿深部找矿中的潜在应用

流体包裹体爆裂法作为一种辅助找矿手段,于20世纪70—80年代曾被前苏联和中国的地质工作者用于找矿勘探实践中,并取得了一定成效。以往许多爆裂法研究表明,矿体所在部位的爆裂强度(频次)较高,而随着远离矿体进入围岩,爆裂频次逐渐降低。一般认为这是由于围绕矿体热液活动强烈和流体包裹体丰度较高所致,因而在矿床(体)及其周围形成蒸发晕正异常。通过对胶西北地区焦家蚀变岩型金矿112线和144线8个钻孔的系统采样和爆裂法测试分析发现,焦家金矿床的花岗岩围岩爆裂曲线具有高的爆裂频次、明显的爆裂峰和高的相变峰,随着围岩蚀变增强,爆裂频次、爆裂峰和相变峰从钾化带经过黄铁绢英岩化带、硅化带到金矿石呈有规律降低,在矿体(化)中心,爆裂频次很低,不显示爆裂峰和相变峰,从而围绕矿体构成蒸发晕负异常。这些爆裂特征,特别是围绕矿体的蒸发晕负异常,对于胶北地区深部金矿找矿勘探具有潜在的应用价值。