内蒙古科右前旗保隆南沟—老敖沟银矿化带岩石特征及其指示意义

内蒙古科右前旗保隆南沟—老敖沟一带银矿受断裂构造控制,矿体多呈脉状,赋存于上侏罗统玛尼吐组和侏罗纪花岗岩体的蚀变岩中.矿化岩石的主要蚀变有钾化、电气石化、绢云母化、硅化、绿泥石化、绿帘石化等.矿石矿物主要有辉银矿、方铅矿、闪锌矿、毒砂、辉钼矿、辉铋矿、黄铁矿、黄铜矿、磁铁矿、褐铁矿等.通过对矿体地质特征、矿化蚀变、矿化...     

塔中原油超高二苯并噻吩硫特征及其控制因素

塔中相当部分原油具有高丰度芳香硫——二苯并噻吩(DBTs)特征,其在原油中的绝对丰度高达26 859μg/g,在芳烃中的相对丰度高达58.2%,主要分布在塔中I号构造带下奥陶统、塔中4(TZ4)和塔中1-6(TZ1-6)井区。采用综合地球化学研究途径,对该区原油的高DBTs特征及其主控因素进行初步探讨。分析表明,研究区母源岩较强地控制DBTs的丰度,纯泥岩、页岩中DBTs丰度不高,灰岩、云岩等烃源岩DBTs丰度偏高或超高;观察到在正常油窗范围内,烃源岩和相关原油随成熟度增加DBTs丰度增加,而塔中型高-过熟原油中DBTs丰度有先增加后减小的趋势,表明热成熟作用对该化合物有较强的控制作用;发现生物降解、水洗可使原油中DBTs丰度降低,但对塔中原油中DBTs影响较小;观测到塔中相当部分原油的DBTs含量与硫酸盐热化学还原作用——TSR的作用产物H2S、硫醇、长链烷基四氢噻烷有一定正相关性。对比研究认为,有多种因素控制塔中原油中DBTs丰度与分布,热成熟作用、TSR是导致塔中下奥陶统部分原油高DBTs特征的重要原因,前者可能是主要因素,特殊母源岩因素相对较少,尽管尚不能排除。TZ4井区等石炭系高DBTs原油主要来自深部地层,与下奥陶统抑或更深层高DBTS原油的混入有关。本研究对于该区深层油气勘探具有重要意义。     

吉林省石头沟区金矿找矿预测

通过对该区地质特征、已知的矿体矿石品位及物探和槽探的综合分析,推断石头沟区还具有可观的资源潜力,依据资源潜力可划分为两个预测靶区,分别为石头沟区南双沟1号矿化蚀变带和小牛圈沟矿化破碎带。其中南双沟1号矿化蚀变带的找矿前景最好,也是最有可能实现找矿突破的靶区,其次为小牛圈沟矿化破碎带也不可忽视。     

615铀矿床蚀变和矿石特征

提出615铀矿床侧缘蚀变的双层交代蚀变结构,即碱性流体交代之后叠加的酸性流体交代蚀变;强调在蚀变带中元素变化与蚀变岩石中矿物之间的相互关系;论述该矿床铀成矿是酸性流体叠加的结果;总结矿床经历了3次不同性质的热流体作用过程：即前期为富硫氢酸期,铀矿化期为氟化物、硫化物、磷酸盐、碳酸盐期和矿后富氧的简单流体作用期。     

河南祁雨沟隐爆角砾岩型金矿床成矿特征浅析

本文以J4隐爆角砾岩体为重点研究对象,从矿床地质、热液蚀变等方面进行分析研究,认为金矿床的形成与浅成-超浅成酸性斑岩侵入体有着密切的成生联系;通过宏观及镜下观察并综合各类蚀变矿物组合之间的关系表明,热液蚀变与金成矿关系密切,蚀变在水平方向及垂直方向上具有分带性。一般而言,在垂直方向上,自岩体中心向上、向下对称分布为：石...     

河南省栾川县南泥湖钼矿成矿特征及找矿远景分析

河南省栾川县南泥湖钼矿是位居世界前列的特大型钼矿之一,分布面积3.98 km2.通过对区域地质背景、矿体地质特征及成矿地质条件的分析研究,总结构造带、小岩体及围岩蚀变与钼成矿的关系,认为南泥湖钼矿床在成因上受构造、岩体、围岩及其蚀变控制明显,并与燕山中期侵入的斑状二长花岗岩关系十分密切.结合以往工程控制程度,提出南泥湖...     

Alteration Geochemistry of Volcanic Rocks around Sarcheshmeh Porphyry Copper Deposit,Rafsanjan, Kerman,Iran: Implications for Regional Exploration

To discriminate the mineral potentiality of the trachybasalt around the Miocene Sarcheshmeh porphyry copper deposit, petrogeochemical characteristics of more than 45 samples of the volcanic rocks were studied. Sarcheshmeh is one of the world's largest Miocene porphyry copper deposits in a continental arc setting and contains about 1200 million tonnes of ores with an average grade of 1.2 percent copper, 0.03 percent molybdenum, 3.9 g/t Ag and 0.11 g/t Au. The biotized and sericitized trachybasalts around the Sarcheshmeh deposit are associated with chalcopyrite, pyrite and molybdenite and and are enriched in Cu (>3108 ppm), K₂O (>4.2%), Rb (>155 ppm) and MgO (>2.9%), but depleted in yttrium (<11 ppm), MnO (<0.06%), CaO (<0.6%), Na₂O (<0.33%), Sr (<107 ppm), and Ba (<181 ppm). The propylitized trachybasalts are enriched in CaO (>9.1%), Na₂O (>3.2%), MnO (>0.24%), Y (>18.2 ppm), and Ba (>323 ppm). The results demonstrate that the diagrams of loss on ignition ? Cu, Cu ? Y, K₂O/K₂O + Na₂O + CaO ? Cu and Y ? MnO may be used as an exploration guide for undiscovered porphyry copper mineralization in the Central Iranian volcano—plutonic copper belt.     

Hydrothermal alteration and K–Ar ages of Neogene‐Quaternary magmatic‐hydrothermal systems at Toyoha‐Muine area in southwest Hokkaido,Japan

This paper presents a review of hydrothermal alteration and K–Ar age data from the Toyoha‐Muine area (TMA), where the Toyoha polymetallic (Ag–Pb–Zn–Cu–In) deposit is located near the Pliocene andesitic volcano that formed Mt Muine. Systematic prospect‐scale mapping, sampling, X‐ray analysis and microscopic observation show that hydrothermal alteration is divided into two groups: acid‐pH and neutral‐pH alteration types. The former is further divided into mineral assemblages I, II and III, while the latter into mineral assemblages IV and V. Different mineralogical features in five mineral assemblages are summarized as follows: (I) Quartz (silicified rock); (II) Pyrophyllite or dickite; (III) Kaolinite or halloysite ± alunite; (IV) Sericite or K‐feldspar; and (V) Interstratified minerals (illite/smectite and chlorite/smectite) and/or smectite. K–Ar radiometric ages determined on twenty‐eight K‐bearing samples (whole volcanic rocks and separated hydrothermal minerals) mainly fall into one of three periods: Early Miocene (24.6–21.4 Ma), Middle–Late Miocene (12.5–8.4 Ma) and Pliocene–Pleistocene (3.2–0 Ma). These three periods are characterized as follows. Early Miocene: A minor hydrothermal activity, which might be genetically related to the intermediate or felsic magmatic activities, formed mineral assemblage IV at 24.6 Ma in the northern part of the TMA. Middle to Late Miocene: The basaltic intrusion, andesitic eruption, and granodiorite intrusions induced hydrothermal activities between 12.5 and 8.4 Ma, resulting in the formation of a mineral assemblage IV with some base metal mineralization. Pliocene–Pleistocene: An andesitic eruption formed Mt Muine between 3.2 and 2.9 Ma. The andesitic activity was associated with acid‐pH mineral assemblages I, II and III locally around the volcano. Latent magmatic intrusions subsequent to the andesitic eruption generated hydrothermal activities that formed mineral assemblages IV and V between 1.9 and 0 Ma in the southern and southeastern parts of Toyoha deposit at depth, overprinting the Middle to Late Miocene alteration. The hydrothermal activities also formed mineral assemblages I, II and III along the Yunosawa fault (east of the Toyoha deposit) and assemblage III in the south and southeast of the Toyoha deposit near the surface.     

Impact cratering on Titan II. Global melt, escaping ejecta, and aqueous alteration of surface organics

New three-dimensional hydrodynamic simulations of hypervelocity impacts into the crust of Titan were undertaken to determine the fraction of liquid water generated on the surface of Saturn's largest moon over its history and, hence, the potential for surface—modification of hydrocarbons and nitriles by exposure to liquid water. We model in detail an individual impact event in terms of ejecta produced and melt generated, and use this to estimate melt production over Titan's history, taking into account the total flux of the impactors and its decay over time. Our estimates show that a global melt layer at any time after the very beginning of Titan's history is improbable; but transient melting local to newly formed craters has occurred over large parts of the surface. Local maxima of the melt are connected with the largest impact events. We also calculate the amount of volatiles delivered at the impact with various impact velocities (from 3 km/s for possible Hyperion fragments to 11 km/s for Jupiter family comets) and their retention as a possible source of Titan's atmosphere. We find the probability of impact ejecta escaping Titan with its modern dense and thick atmosphere is rather low, and dispersal of Titan organics throughout the rest of the Solar System requires impactors tens of kilometers in diameter. Water ice melting and exposure of organics to liquid water has been widespread because of impacts, but burial or obscuration of craters by organic deposits or cryovolcanism is aided by viscous relaxation. The largest impactors may breach an ammonia-water mantle layer, creating a circular albedo contrast rather than a crater.     

SIMULATED THERMAL ALTERATION OF STEROLS AND KETO-ALCOHOLS IN MARINE SEDIMENTS OF THE OKINAWA TROUGH

Compositional data on the sterol and alcohol fractions isolated from deep-sea marine sediments from the Okinawa Trough were obtained to determine the relative contribution from. marine and terrestrial inputs. Following extraction, the sterol plus alcohol fraction was isolated by layer chromatography, derivatized with BSTFA and then analysed by capillary GC and GC-MS. A suite of C26-C29 stenols and stanols and C30-C32 keto - alcohols were identified in the sediments. The thermal stability of the compounds in these sediments was studied by heating portions of the surface sediment in glass tubes fpr 16 hours at temperatures from 50℃ to 200℃.The C27 stanol/stenol ratio increased when temperatures went up to 175℃ , but the distribution of C30-C32 Keto - alcohols remained unaffected. At 200℃ most of the sterols and Keto - alcohols were destroyed.