Revised activity–composition models for clinopyroxene and amphibole

Recent activity–composition models for clinopyroxene and amphibole are revised to provide better consistency with observed phase relations in natural rocks. For clinopyroxene, the calibration in NCFMAS is retained, but the incorporation of acmite is revised to improve the partitioning of ferric iron between coexisting clinopyroxenes. For amphibole, the NCFMASH calibration is retained, but the addition of ferric iron is changed to provide consistency with the clinopyroxenes. The thermodynamics of orthoamphibole (gedrite) is also adjusted to resolve an unrelated inconsistency. The effects of these improvements are illustrated through comparison of calculated pseudosections produced with the existing and new models with natural data from lawsonite eclogites.     

Application of stress mapping in cross‐section to understanding ore geometry,predicting ore zones and development of drilling strategies

Stress mapping is a numerical modelling technique used to determine the distribution and relative magnitude of stress during deformation in a mineralised terrane. It is based on the general principle that fluid flow in the Earth's crust is primarily related to pressure gradients. It is best applied to epigenetic hydrothermal mineral deposits, where fluid flow and fluid flux are enhanced in dilational sections of structures and in sites of enhanced rock permeability due to high fracture density. These are defined by sites of low minimum principal stress (σ₃). Most stress mapping is carried out in two dimensions in plan view using geological maps. This is suitable for terranes with steeply dipping lithostratigraphy and structures in which the distribution of mineral deposits is largely controlled by fault structures portrayed on the maps. However, for terranes with gently dipping sequences and structures, and for situations where deposits are sited in and near the hinges of complex fold structures, stress mapping in cross‐section is preferable. The effectiveness of stress mapping is maximised if mineralisation was late in the evolutionary history of the host terrane, and hence the structural geometry of the terrane and contained deposits were essentially that expressed today. The orientation of syn‐mineralisation far‐field stresses must also be inferred. Two examples of orogenic gold deposits, which meet the above criteria, are used to illustrate the potential of stress mapping in cross‐section. Sunrise Dam, located in the Archaean Yilgarn Craton, is a lode‐gold deposit sited in a thrust‐fold belt. Stress mapping illustrates the heterogeneity of stress distribution in the complex structural geometry of the deposit, and predicts the preferential siting of ore zones around the intersections of more steeply dipping, linking thrusts and banded iron‐formation units, and below the controlling more gently dipping basal thrust, the Sunrise Shear. The Howley Anticline in the Pine Creek block hosts several Palaeoproterozoic gold deposits, sited in complex anticlinal structures in greywacke sequences. Stress mapping indicates that gold ores should develop in the hinge zones of symmetrical anticlines, in the hinge zones and more steeply dipping to overturned limbs of asymmetric anticlines, and in and around thrusts in both anticlines and parasitic synclines. The strong correlation between the predictions of the stress mapping, based on the distribution of low σ₃, and the location of gold ores emphasises the potential of stress mapping in cross‐section, not only as an exploration tool for the discovery of additional resources or deposits, but also as a test of geological models. Knowledge of the potential siting of gold ores and their probable orientations also provides a guide to drilling strategies in both mine‐ and regional‐scale exploration.     

西藏羊八井地热田水热蚀变

本文对羊八井地热田钻扎ZK-201、ZK-301和ZK-308的岩心进行了较系统的蚀变矿物学、岩石学和流体包体研究。划分出6个蚀变矿物共生组合及蚀变分带,讨论了蚀变过程中岩石化学变化的特点,并推测了蚀变的温度和酸碱度条件。研究表明,热田曾处于极度的活动状态,最高温度达220-240℃,由于冷水的入侵,热田在目前钻探所及范围已冷却了50-70℃。蚀变矿物分布模式表明,目前热田流体主通道位于北部,热田进一步的开发应以寻找北部深部高温流体为主。     

青海湖沉积物中的粘土矿物

本文对青海湖沉积物中的粘土矿物和沉积环境进行了初步研究。沉积物的粒度成分一般以粉砂级为主,湖周沉积物较粗,湖内沉积物较细。湖中粘土矿物以伊利石-绿泥石为主,含少量蒙脱石和高岭石等。沉积物表层未见蒙脱石,粘土中Al₂O₃、K₂O和MgO的相对百分含量的特征与海粘土的化学成分特征相似。     

广东省海岸表层沉积物的重矿物特征及其与沉积环境的关系

广东省海岸表层沉积物中的重矿物近40种。含量较高的有钛铁矿、赤矿铁、磁铁矿、话石、电气石、黑云母和普通角闪石等。自生矿物主要为硬石膏、自然铜、黄铁矿及菱铁矿。这些矿物来自附近的母岩。根据物源性质不同,可将不同岸段重矿物区分为陆源矿物组合、近源-自生矿物组合和近源矿物组合三种:除物源控制外,重矿物含量、种类、形态特征及其在平面上的分布主要受沉积环境影响。据此,可将重矿物分布类型划分为河口型、海湾型和海岛型三类,且与上述不同矿物组合性质相对应。     

铈硼硅石的微量化学分析法

铈硼硅石是一种罕见的稀土矿物,由于它含有某些化学性质近似的元素,故分析难度较大。本文研究了应用纸色层法和离子选择性电极法对铈硼硅石中某些主要成分和微成分的分离和测定条件,设计了较合理的铈硼硅石微量全分析流程。该流程也适合类似矿物的分析,与常法比较,本法具有快速、准确、成本低和用样少等优点。     

我国首次发现的纤碳铀矿

本文报道的纤碳铀矿产于湖南某花岗岩型铀矿床氧化带中。纤碳铀矿是一种铀酰碳酸盐矿物,在中国是首次发现。本文作了系统的矿物研究并与国外资料作了对比。     

米仓山碱性岩中的主要矿物研究及其成因信息

米仓山碱性岩中的主要矿物为富铝的(次硅)铝铁质透辉石、钙质角闪石、霞石等,且大量出现霞石,但无或极少有碱性暗色矿物。研究表明:氧逸度低是碱性岩浆不能结晶出碱性暗色矿物的原因。本区这种无碱性暗色矿物的碱性岩是在封闭体系及深成条件下结晶的,而其它地区含有碱性暗色矿物的岩石则是在开放体系中形成的。     

Mineral composition variation in Alpine Schist, Southern Alps, New Zealand: Implications for recrystallization and exhumation

Abstract Compositional variation of silicates (plagioclase, K-feldspar, epidote, titanite, garnet, white mica, biotite, chlorite), ilmenite, carbonates (calcite, ankerite) and apatite, in quartzofeldspathic lithologies of the Alpine Schist, New Zealand, is discussed in terms of increasing metamorphic grade and possible isograd-producing reactions. The mineral data, in conjunction with geological considerations, are used to determine polychronous P-T arrays of an early high P/T event (c. 16°C/kb; 5°C/km) overprinted by a lower P/T event (c. 50°C/kb; 15°C/km) that provides an estimation of Mesozoic and Cenozoic exhumation of schist of 11 to 13 km and 19 to 22 km respectively. The effects of possible shear heating and recrystallization to form K-feldspar zone schist near the Alpine Fault is consistent with movement along a mid to lower crustal detachment surface during Cenozoic shortening, and near isothermal exhumation of the schists to form the Southern Alps.     

塞北雪（锂—锶—偏硅酸）珍贵天然矿泉水

经勘察评价和国家级评审鉴定，天镇县城关Ｔ＿（６７）井属锂－锶－偏硅酸三项达标的复合型优质饮用天然矿泉水。矿泉水产于近东西向挽近断裂带上，马圈痒地热田边部，地势平坦，环境无污染，交通便利，水质独特，水量丰富，具有综合开发优势，适宜建厂开发。