观驾山—黑岛一带信息量法找金研究     

简文星  吕贻峰  秦松贤  刘吉平 《国土资源》1996,(2)

本文以成矿地质模型为依据，对观驾山—黑山岛一带的化探、物探、遥感及地质等信息变量进行了详细的分析，选取了１０个信息变量２４个标志状态；在此基础上，运用信息量法对研究区内４５８个单元的信息量值进行计算，并由此确定了研究范围内的成矿远景区。事实表明，研究区信息量成矿预测是非常有效的  相似文献   

甘新蒙北山地区成矿带划分和基本特征对比   总被引：3，自引：1，他引：2  

彭巨贵  张发荣  赵福昌 《地球科学与环境学报》2006,28(3):11-18

在对甘新蒙北山地区成矿地质背景和成矿在时空上的联系性等综合研究分析基础上,运用新理论、新认识,以板块构造单元划分为基础,将本区划分为3个Ⅲ级成矿带、11个Ⅳ级成矿带,并对Ⅲ级成矿带特征进行了阐述,以期为矿产勘查和地质大调查工作部署提供新的思路和依据。进一步就主要矿床(点)、构造单元、矿种、赋矿建造、控矿因素、成矿类型、成矿时代等方面进行了对比,认为各Ⅳ级成矿带在区域上具有相对稳定的展布范围,具有相同的构造环境和成矿条件、类似的矿种和成矿时代,存在一定的相似性、可比性,并且各成矿带具有一定的潜在找矿价值。  相似文献   

青海省沙柳河南区有色金属矿成矿物质来源及矿床成矿模式探讨     

马永铨  姜洪成 《青海国土经略》1994,(1)

本文简述了沙柳河南区有色金属矿床的基本特征。通过对成矿热液及成矿物质的来源与性质的研究,认为该矿床的成因类型为火山沉积—接触交代改造叠加型,进而探讨了该矿床的成矿模式。  相似文献   

Metamorphism in Archaean greenstone belts: calculated fluid compositions and implications for gold mineralization     

R. POWELL  T. M. WILL  G. N. PHILLIPS 《Journal of Metamorphic Geology》1991,9(2):141-150

An inescapable consequence of the metamorphism of greenstone belt sequences is the release of a large volume of metamorphic fluid of low salinity with chemical characteristics controlled by the mineral assemblages involved in the devolatilization reactions. For mafic and ultramafic sequences, the composition of fluids released at upper greenschist to lower amphibolite facies conditions for the necessary relatively hot geotherm corresponds to those inferred for greenstone gold deposits (X_CO2= 0.2–0.3). This result follows from the calculation of mineral equilibria in the model system CaO–MgO–FeO–Al₂O₃–SiO₂–H₂O–CO₂, using a new, expanded, internally consistent dataset. Greenstone metamorphism cannot have involved much crustal over-thickening, because very shallow levels of greenstone belts are preserved. Such orogeny can be accounted for if compressive deformation of the crust is accompanied by thinning of the mantle lithosphere. In this case, the observed metamorphism, which was contemporaneous with deformation, is of the low-P high-T type. For this type of metamorphism, the metamorphic peak should have occurred earlier at deeper levels in the crust; i.e. the piezothermal array should be of the ‘deeper-earlier’type. However, at shallow crustal levels, the piezothermal array is likely to have been of ‘deeper-later’type, as a consequence of erosion. Thus, while the lower crust reached maximum temperatures, and partially melted to produce the observed granites, mid-crustal levels were releasing fluids prograde into shallow crustal levels that were already retrograde. We propose that these fluids are responsible for the gold mineralization. Thus, the contemporaneity of igneous activity and gold mineralization is a natural consequence of the thermal evolution, and does not mean that the mineralization has to be a consequence of igneous processes. Upward migration of metamorphic fluid, via appropriate structurally controlled pathways, will bring the fluid into contact with mineral assemblages that have equilibrated with a fluid with significantly lower X_CO2. These assemblages are therefore grossly out of equilibrium with the fluid. In the case of infiltrated metabasic rocks, intense carbonation and sulphidation is predicted. If, as seems reasonable, gold is mobilized by the fluid generated by devolatilization, then the combination of processes proposed, most of which are an inevitable consequence of the metamorphism, leads to the formation of greenstone gold deposits predominantly from metamorphic fluids.  相似文献   

新疆北部后碰撞与幔源岩浆有关的成矿谱系   总被引：18，自引：12，他引：6  

王京彬  王玉往  周涛发 《岩石学报》2008,24(4)

新疆北部与后碰撞幔源岩浆作用有关的矿床主要有四类:铜镍硫化物矿床、钒钛磁铁矿矿床、钛铁矿-铜镍硫化物复合矿床和玄武岩型自然铜矿床。上述四类矿床成矿时代相近(主成矿期为二叠纪),空间相邻,跨构造单元分布,彼此之间可出现过渡或复合矿床类型,构成了独特的后碰撞与幔源岩浆作用有关的成矿谱系,也是中亚型造山后碰撞阶段颇具特色的成矿组合。依据其成矿专属性的不同,新疆北部与幔源岩浆有关的矿床可分为两个系列:钛铁系列和铜镍系列。钛铁系列以尾亚矿床为代表,以高钛富碱为特征,为碱性系列,REE总量高,LREE富集,ε_(Nd)(t)近0值,其含矿岩体的地球化学特征与峨嵋大火成岩省钒钛磁铁矿含矿岩体特征一致,推测其含矿岩浆来源与地幔柱活动有关;而以黄山、喀拉通克为代表的铜镍矿床成矿岩体,以相对富镁为特征,属钙碱系列和拉斑玄武岩系列,REE总量较低,模式曲线呈LREE略富集的平缓型分布,ε_(Nd)(t)为明显的正值,可能来自亏损岩石圈地幔的部分熔融。新疆北部后碰撞阶段除发育了与幔源岩浆有关的成矿谱系外,还发育了与造山带有关的构造-岩浆-成矿体系。这种既有地幔柱成矿又有造山带成矿的双重特性,可能是二叠纪地幔柱活动与造山(后碰撞)作用叠加的结果。  相似文献   

黑龙江省鸡西盆地南、北两带城子河组精细对比     

王金山 《中国煤炭地质》2008,(8):5-9

鸡西盆地被平麻断裂分割成南、北两个条带,多数研究者将南带1煤之下的海相层叠伏于北带海相层或底砾岩之下,称为“城子河组下段”或“石河北组”。利用事件地层学的原理,分析盆地内城子河组早期盆地裂陷、海侵、火山喷发、聚煤等重大事件在地层精细对比方面的意义,甄别出了盆地中重大事件的地层记录．以等时层为基础建立对比框架。通过大量钻井资料追溯对比,认为盆地中坳陷部位的渴湖海湾沉积是南北两带的沉积过渡类型,根据微体古生物研究,南北两带海相层中的沟鞭藻类化石面貌基本一致,南北带的海相层应是同一层位,初步实现了盆地内南、北两个条带城子河组的精细对比,为恢复盆地古地理环境奠定了可靠的基础。  相似文献   

地铁施工对济南白泉泉群流量的影响     

束龙仓  王小博  李虎  倪寒茜  李罡  余亚飞  王鑫  张曼琦 《吉林大学学报(地球科学版)》2021,51(1):192-200

为研究地铁建设对济南白泉泉群的影响，在综合分析白泉泉域地质、水文地质条件的基础上，假定研究区岩溶强径流带位置及水力性质，利用FEFLOW软件建立地下水流数值模型。以规划地铁M1号线为研究对象，分析了济南东站、梁王站、梁王东站分别施工及3个站同时施工4种情景下，采用施工降水或施工降水+人工回灌两种施工方式对白泉泉群流量的影响。结果表明：单独采用施工降水的施工方式使得白泉泉群流量衰减，其中3个站同时施工对泉流量的影响最大，泉流量最大衰减达5.48%；各站分别施工时，济南东站对泉流量影响最大，泉流量较未施工时减少了0.043×10⁴ m³/d。采用施工降水+人工回灌的施工方式，能够有效缓解泉流量的衰减，各车站施工时的泉流量衰减由仅施工降水时的2.26%~5.48%降低至0.08%~1.21%。岩溶强径流带有利于地下水形成优势径流，促进白泉泉群补给，一定程度上缓解因地铁施工引起的泉流量衰减。  相似文献   

地学“开合律”及其在造山带研究中的意义   总被引：14，自引：2，他引：12  

杨巍然 《地质科技情报》1992,11(3):5-9

“开合律”是地学辩证法基本规律之一。本文概述了它的内容与特点,阐明它在造山带研究中的意义及运用它指导造山带研究的步骤,并根据目前已总结的5种“开”、“合”类型相应地提出了5种造山带类型。  相似文献   

Preservation/exhumation of ultrahigh-pressure subduction complexes   总被引：14，自引：0，他引：14  

W.G. Ernst   《Lithos》2006,92(3-4):321-335

Ultrahigh-pressure (UHP) metamorphic terranes reflect subduction of continental crust to depths of 90–140 km in Phanerozoic contractional orogens. Rocks are intensely overprinted by lower pressure mineral assemblages; traces of relict UHP phases are preserved only under kinetically inhibiting circumstances. Most UHP complexes present in the upper crust are thin, imbricate sheets consisting chiefly of felsic units ± serpentinites; dense mafic and peridotitic rocks make up less than  10% of each exhumed subduction complex. Roundtrip prograde–retrograde P–T paths are completed in 10–20 Myr, and rates of ascent to mid-crustal levels approximate descent velocities. Late-stage domical uplifts typify many UHP complexes.

Sialic crust may be deeply subducted, reflecting profound underflow of an oceanic plate prior to collisional suturing. Exhumation involves decompression through the P–T stability fields of lower pressure metamorphic facies. Scattered UHP relics are retained in strong, refractory, watertight host minerals (e.g., zircon, pyroxene, garnet) typified by low rates of intracrystalline diffusion. Isolation of such inclusions from the recrystallizing rock matrix impedes back reaction. Thin-aspect ratio, ductile-deformed nappes are formed in the subduction zone; heat is conducted away from UHP complexes as they rise along the subduction channel. The low aggregate density of continental crust is much less than that of the mantle it displaces during underflow; its rapid ascent to mid-crustal levels is driven by buoyancy. Return to shallow levels does not require removal of the overlying mantle wedge. Late-stage underplating, structural contraction, tectonic aneurysms and/or plate shallowing convey mid-crustal UHP décollements surfaceward in domical uplifts where they are exposed by erosion. Unless these situations are mutually satisfied, UHP complexes are completely transformed to low-pressure assemblages, obliterating all evidence of profound subduction.  相似文献   

Evolution from Oceanic Subduction to Continental Collision: a Case Study from the Northern Tibetan Plateau Based on Geochemical and Geochronological Data   总被引：41，自引：0，他引：41  

SONG  SHUGUANG; ZHANG  LIFEI; NIU  YAOLING; SU  LI; SONG  BIAO; LIU  DUNYI 《Journal of Petrology》2006,47(3):435-455

Two apparently distinct, sub-parallel, paleo-subduction zonescan be recognized along the northern margin of the Tibetan Plateau:the North Qilian Suture Zone (oceanic-type) with ophioliticmélanges and high-pressure eclogites and blueschistsin the north, and the North Qaidam Belt (continental-type) inthe south, an ultrahigh-pressure (UHP) metamorphic terrane comprisingpelitic and granitic gneisses, eclogites and garnet peridotites.Eclogites from both belts have protoliths broadly similar tomid-ocean ridge basalts (MORB) or oceanic island basalts (OIB)in composition with overlapping metamorphic ages (480–440Ma, with weighted mean ages of 464 ± 6 Ma for North Qilianand 457 ± 7 Ma for North Qaidam), determined by zirconU–Pb sensitive high-resolution ion microprobe dating.Coesite-bearing zircon grains in pelitic gneisses from the NorthQaidam UHP Belt yield a peak metamorphic age of 423 ±6 Ma, 40 Myr younger than the age of eclogite formation, anda retrograde age of 403 ± 9 Ma. These data, combinedwith regional relationships, allow us to infer that these twoparallel belts may represent an evolutionary sequence from oceanicsubduction to continental collision, and continental underthrusting,to final exhumation. The Qilian–Qaidam Craton was probablya fragment of the Rodinia supercontinent with a passive marginand extended oceanic lithosphere in the north, which was subductedbeneath the North China Craton to depths >100 km at c. 423Ma and exhumed at c. 403 Ma (zircon rim ages in pelitic gneiss). KEY WORDS: HP and UHP rocks; subduction belts; zircon SHRIMP ages; Northern Tibetan Plateau  相似文献