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

Alijan Aftabi  Habibeh Atapour 《Resource Geology》2011,61(1):76-90

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.  相似文献   

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

Toru SHIMIZU  Masahiro AOKI 《Resource Geology》2011,61(2):192-209

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.  相似文献   

植被覆盖区高光谱蚀变矿物信息提取   总被引：2，自引：1，他引：1  

吕凤军  郝跃生  王娟  姚佛军 《吉林大学学报(地球科学版)》2011,41(1):316-321

在植被覆盖严重地区,基于综合光谱信息模型,开展了高光谱遥感典型蚀变矿物信息提取研究.以河北省承德市大营子地区为例,利用Hyperion数据,在植被覆盖度大于70%的地区,根据蚀变矿物与背景地物波谱特征的差异,提取了该区绿泥石、斜绿泥石、方解石和白云石蚀变矿物分布信息,与已知地质矿产资料及野外检查结果一致.最后依据蚀变矿...  相似文献   

平湖油气田油气成藏新模式   总被引：2，自引：0，他引：2  

王伟  张丽艳  李响 《海相油气地质》2011,16(1):51-55

通过对区域构造演化、沉积背景、盖层特性以及油气生成和运聚条件等的分析,结合前人研究成果,重新建立了平湖油气田的成藏模式.平湖油气田含上部渐新统花港组和下部始新统平湖组两套储层,呈上油下气的油气分布特征.古新世-始新世的断块阶段在区域上初步形成了大断裂控制下的断背料构造,在平湖组形成圈闭.中新世中期(平湖组沉积后期)发生...  相似文献   

新疆和静县查岗诺尔铁矿床FeⅠ矿体围岩蚀变特征     

陈文革  张海军  刘铭峰 《西北地质》2011,44(2):94-101

新疆和静县查岗诺尔铁矿床位于伊犁微板块北缘之博洛科努早古生代岛弧带,属于阿吾拉勒金、铜、铅、锌、铁成矿带东段。矿区出露地层主要为下石炭统大哈拉军山组火山岩和上石炭统伊什基里克组火山岩,两者为断层接触关系。由于成矿矿浆的多期次活动,查岗诺尔铁矿广泛发育围岩蚀变,形成沿断裂带分布的带状蚀变带。通过研究发现,矿床主矿体FeⅠ号主矿体的围岩蚀变情况,按不同蚀变矿物组合,自东向西可分出石榴石带、绿帘石-阳起石带、阳起石-磁铁矿带、蚀变大理岩带和阳起石带,对应三期蚀变作用。各阶段的矿物共生组合分别为：磁铁矿＋透辉石＋石榴石、磁铁矿＋阳起石＋绿帘石、磁铁矿-石榴石-阳起石-绿帘石-石英-碳酸盐。矿区蚀变是由高、中温火山热液交代中酸性火山碎屑岩而形成。  相似文献   

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

Natalia Artemieva  Jonathan I. Lunine 《Icarus》2005,175(2):522-533

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.  相似文献   

秦巴造山带构造特征与地壳深部构造     

王全庆 《地球科学与环境学报》1993,(4)

秦巴造山带是夹持在华北古陆与扬子古陆之间的印支期陆内造山带。其内部自北而南可分为北秦岭变质-构造-岩浆岩构造带、中秦岭褶皱构造带及南秦岭伸展-滑脱构造带等三大不同构造面貌及演化过程、不同物质建造差异的构造单元。  相似文献   

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

姜善春  John K.Volkman  Teresa O''''Leary  张惠之  栾作峰 《中国海洋湖沼学报》1993,(4)

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.  相似文献   

Cordierite-anthophyllite rocks from north-west Queensland, Australia: metamorphosed magnesian pelites     

J. REINHARDT 《Journal of Metamorphic Geology》1987,5(4):451-472

Abstract Cordierite-anthophyllite rocks and related cordierite-rich, talc-rich and chlorite-rich rocks occur in the Rosebud Syncline, north-west Queensland, Australia, as part of a Proterozoic metasedimentary sequence. Field relations and rock compositions attest the sedimentary origin of these rather unusual metamorphic rocks. Their chemical composition is comparable to that of unmetamorphosed, alkali- and Ca-poor pelites, which are associated with some evaporite deposits. Other occurrences of cordierite-anthophyllite rocks have commonly been interpreted as metamorphosed chloritic alteration products derived from mafic or felsic volcanics. A comparative chemical study, using analyses of cordierite-anthophyllite rocks from such alteration zones and analyses of unmetamorphosed magnesian pelites, demonstrates the general chemical similarity between these two rock groups of entirely different origin. However, distinct differences in major element relations help to distinguish these two genetic groups. Particularly useful are Al₂O₃–FeO–MgO plots, in which evaporitic pelites occupy the Fe-poor side. The highly magnesian metamorphic rocks from the Rosebud Syncline fall entirely into the compositional field of evaporitic clays and shales. Furthermore, analyses of relatively immobile trace elements give supporting evidence for the sedimentary origin of these cordierite-anthophyllite rocks. The correlation with trace element ranges of clays and shales is very good. However, the correlation with trace element ranges of mafic and felsic volcanics is poor, and major discrepancies occur with Cr, Ni, Co, Nb, Sc, Th and Ti. Thus, the magnesian metamorphics of the Rosebud Syncline appear to be derived from evaporitic clays rich in magnesian clay minerals, such as palygorskite, sepiolite, chlorite or corrensite. The complete metamorphic rock assemblage of interlayered calcareous, aluminous and magnesian rocks is interpreted as a metamorphosed carbonate-evaporite-pelite sequence.  相似文献   

Correspondence analysis applied to a comparison of some rhyolitic zones in the Noranda area (Quebec, Canada)     

Christina Dumitriu  Roger Webber  Michel David 《Mathematical Geology》1979,11(3):299-307

Correspondence analysis was applied to 177 chemical analyses (major elements) of rocks from some rhyolitic zones of the Noranda area (Quebec). The objective was to grade the individual sample sections with respect to their attractiveness considering the chemical alterations related to mineralization. The results obtained show that it is possible to differentiate sections from different rhyolitic horizons.  相似文献