Early Cretaceous U–Pb zircon ages for the Copiapó plutonic complex and implications for the IOCG mineralization at Candelaria, Atacama Region, Chile     

Robert Marschik  Frank Söllner 《Mineralium Deposita》2006,41(8):785-801

Four of the major plutons in the vicinity of the Candelaria mine (470 Mt at 0.95% Cu, 0.22 g/t Au, 3.1 g/t Ag) and a dike–sill system exposed in the Candelaria open pit have been dated with the U–Pb zircon method. The new geochronological data indicate that dacite magmatism around 123 Ma preceded the crystallization of hornblende diorite (Khd) at 118 ± 1 Ma, quartz–monzonite porphyry (Kqm) at 116.3 ± 0.4 Ma, monzodiorite (Kmd) at 115.5 ± 0.4 Ma, and tonalite (Kt) at 110.7 ± 0.4 Ma. The new ages of the plutons are consistent with field relationships regarding the relative timing of emplacement. Plutonism temporally overlaps with the iron oxide Cu–Au mineralization (Re–Os molybdenite ages at ∼115 Ma) and silicate alteration (ages mainly from 114 to 116 and 110 to 112 Ma) in the Candelaria–Punta del Cobre district. The dated dacite porphyry and hornblende diorite intrusions preceded the ore formation. A genetic link of the metallic mineralization with the quartz–monzonite porphyry and/or the monzodiorite is likely. Both of these metaluminous, shoshonitic (high-K) intrusions could have provided energy and contributed fluids, metals, and sulfur to the hydrothermal system that caused the iron oxide Cu–Au mineralization. The age of the tonalite at 110.7 Ma falls in the same range as the late alteration at 110 to 112 Ma. Tonalite emplacement may have sustained existing or driven newly developed hydrothermal cells that caused this late alteration or modified ⁴⁰Ar/³⁹Ar and K/Ar systematic in some areas.  相似文献   

Variscan ore formation and metamorphism at the Felbertal scheelite deposit (Austria): constraining tungsten mineralisation from Re–Os dating of molybdenite     

Johann G. Raith  Holly J. Stein 《Contributions to Mineralogy and Petrology》2006,152(4):505-521

The Felbertal scheelite deposit in the Eastern Alps has been regarded as the type locality for stratabound scheelite deposits. It is hosted by a Cambro-Ordovician metavolcanic arc sequence with minor Variscan granitoids (∼ 340 Ma) in the central Tauern Window. Re–Os model ages for molybdenite from the Felbertal tungsten deposit range between ∼ 358 and ∼ 336 Ma and record several pulses of magmatic-hydrothermal-metamorphic molybdenite formation. Molybdenite ages from the K2 orebody, a scheelite-rich quartz mylonite in the Western ore field, indicate that both mineralisation and mylonite are Variscan in age and suggest that the shear zone was active for ∼ 20 million years. Early stage tungsten mineralisation (Scheelite 1) in quartzitic ores in the Eastern ore field, which is free of molybdenite, yielded very low to near blank levels of Re and Os and thus could not be dated. However, molybdenite from scheelite–quartz stringers, previously interpreted as a feeder stockwork to quartzitic scheelite ore of presumed Cambrian age, yielded Variscan Re–Os ages of ∼ 342 and ∼ 337 Ma. Dating of molybdenite contained in scheelite ores thus far provides no indication of a Cambrian component to the tungsten mineralisation. Our data are consistent with a model of either granite intrusion-related ore formation and coeval metamorphic overprint during the Early Carboniferous or, alternatively, molybdenite formation may be exclusively attributed to Variscan metamorphism (see Stein 2006).  相似文献   

Paleoproterozoic accretion in the Northeast Siberian craton: Isotopic dating of the Anabar collision system   总被引：1，自引：0，他引：1  

O. M. Rosen  L. K. Levskii  D. Z. Zhuravlev  A. Ya. Rotman  Z. V. Spetsius  A. F. Makeev  N. N. Zinchuk  A. V. Manakov  V. P. Serenko 《Stratigraphy and Geological Correlation》2006,14(6):581-601

Geochronological database considered in the work and characterizing the Anabar collision system in the Northeast Siberian craton includes coordinated results of Sm-Nd and Rb-Sr dating of samples from crustal xenoliths in kimberlites, deep drill holes, and bedrock outcrops. As is inferred, collision developed in three stages dated at 2200–2100, 1940–1760, and 1710–1630 Ma. The age of 2000–1960 Ma is established for substratum of mafic rocks, which probably originated during the lower crust interaction with asthenosphere due to the local collapse of the collision prism. Comparison of Sm-Nd and Rb-Sr isochron dates shows that the system cooling from ≈700 to ≈300°C lasted approximately 300 m.y. with a substantial lag relative to collision metamorphism and granite formation. It is assumed that accretion of the Siberian craton resulted in formation of a giant collision mountainous structure of the Himalayan type that was eroded by 1.65 Ga ago, when accumulation of gently dipping Meso-to Neoproterozoic (Riphean) platform cover commenced.  相似文献   

青藏高原唐古拉山口第四纪冰碛层划分及其地质环境意义   总被引：4，自引：1，他引：4       下载免费PDF全文

段志明  李勇  李亚林  张毅王谋 《中国地质》2005,32(1):128-134

在对唐古拉山口现代冰川和古冰川考察研究的基础上，结合定位观测资料和TL、^10B-^26Al-^21Ne及^14C测年数据，对区内第四纪冰川遗迹进行了深入讨论，划分出二次冰期(即中更新世晚期的倒数第二次冰期、晚更新世中一晚期的末次冰期)和二次全新世冰进(即新冰期和小冰期)。提出在早更新世时，由于山体未达到当时冰川发育的雪线高度，所以未发育冰川。但在唐古拉山口地区，截止目前还未找到中更新世早期的倒数第三次冰期的冰川遗迹，由于高原隆升的滞后性和冰川发育的延滞效应及“亚洲干极”的耦合，推测仍只发育局部冰川作用。进一步研究表明，古今雪线由高原边缘向腹地升高，唐古拉山地区高出边缘1500m左右，生动表现了“亚洲干极”的作用；广泛分布的湖群说明羌塘地区是一个大江大河尚未伸入的内流地区，意味着青藏高原是个年青的高原。由于青藏高原的隆升，对高原腹地引起的干旱化过程和水分严重不足，使唐古拉山地区的冰川自倒数第二次冰期以来，冰川规模一次比一次明显地减小。  相似文献   

内蒙古中部苏尼特左旗富钾花岗岩锆石SHRIMP U-Pb年龄   总被引：12，自引：3，他引：12  

石玉若  刘敦一简平　张旗张福勤  苗来成施光海  张履桥陶华 《地质通报》2005,24(5):424-428

精确的锆石SHRIMP U-Pb年龄测定表明,内蒙古苏尼特左旗富钾花岗岩的结晶年龄分别为423Ma±8Ma和424Ma±10Ma.综合区域资料,认为该年龄代表了内蒙古中部志留纪期间发生弧-陆碰撞事件的时限.  相似文献   

河南焦作云台山早前寒武纪变质基底锆石SHRIMP U-Pb年龄   总被引：4，自引：0，他引：4  

高林志  赵汀  万渝生  赵逊  马寅生  杨守政 《地质通报》2005,24(12):1089-1093

应用离子探针技术,对华北太行山南缘钾长石化长英质副片麻岩和钾长石化片麻状奥长花岗岩进行了锆石年龄测定。钾长石化长英质副片麻岩的变质原岩为泥砂质碎屑沉积岩,其形成时代很可能为新太古代。碎屑锆石普遍存在强烈铅丢失,靠近上交点的5个数据点207Pb/206Pb加权平均年龄为3399Ma±8Ma,代表了物源区组成的时代。钾长石化片麻状奥长花岗岩2组锆石207Pb/206Pb加权平均年龄分别为2511Ma±13Ma(岩体形成时代)和2735Ma±16Ma(残余锆石年龄),分别代表该岩体形成时代和残余锆石年龄。新的资料支持了华北克拉通中部造山带太古宙地质体与其东部陆块存在亲缘关系的认识。  相似文献   

松潘-甘孜地体内花岗岩锆石SHRIMP U-Pb定年及其构造意义   总被引：36，自引：17，他引：36  

胡健民孟庆任  石玉若渠洪杰 《岩石学报》2005,21(3):867-880

松潘-甘孜地体总体上是一个三角状褶皱带,其北侧、东南侧及东侧分别与东昆仑-西秦岭构造带、金沙江构造带及龙门山构造带相邻。地体内几乎全部被三叠系浊积岩所覆盖,其中侵位了很多花岗岩体。显然,这些花岗岩的岩浆特征、来源与侵位时代,对研究松潘-甘孜地体基底性质、构造演化等问题具有重要意义。本文报道利用SHRIMP定年技术对一些花岗岩岩体锆石所进行的精确测年数据。测试结果表明:(1)松潘-甘孜地体内的花岗岩体主要形成于晚三叠世,但岩浆活动可延续到早侏罗世晚期;(2)早期花岗岩浆活动与三叠纪系褶皱变形大致同期,指示这一时期的花岗岩浆的形成可能与三叠系下部大型拆离滑脱构造相关;(3)花岗岩结晶锆石普遍具有浑圆状或不规则状较老的继承锆石核,这些核部继承锆石可能代表花岗岩浆在上升过程中从不同地层内捕获的碎屑锆石,或者是下地壳岩石深熔残留锆石。根据SHRING U-Pb定年,这些继承锆石的年龄分别为二叠纪、加里东期、晚元古代和早元古代。元古代碎屑锆石的存在也可能指示松潘-甘孜地体具前寒武系基底。  相似文献   

冷暖事件对大气能量循环和纬向平均环流影响的模拟研究   总被引：1，自引：0，他引：1  

张韬  吴国雄  郭裕福 《气象学报》2002,60(5):513-526

利用中国科学院大气物理研究所大气科学与地球流体力学数值模拟国家重点实验室新发展的GOALS 5全球海 陆 气耦合模式研究了暖事件 (ElNi no)和冷事件 (LaNina)对大气能量循环和纬向平均环流的影响 ,并用观测资料进行了对比分析。结果表明 :对于纬向平均资料来说 ,冷、暖事件在热带和副热带地区的大气环流相关量的反相变化特征非常清晰 ,中高纬度地区并不明显。此外 ,还发现 ,暖事件时定常涡动的经向热通量的变化是北半球对流层热带外地区温度异常的主要原因 ,而瞬变波的影响则起抵消作用。冷事件时定常波和瞬变波相互抵消的局地特征也依然存在 ,但瞬变波的影响有所增强。  相似文献   

同位素地质学定年方法评述   总被引：16，自引：1，他引：16  

赵玉灵  杨金中等 《地质与勘探》2002,38(2):63-67

详细分析了当前同纱年代学的常用定年方法，如K-Ar法，U-Pb法，Rb-Sr法和Sm-Nd法等的适用性和局限性。讨论了地质事件定年过程中存在的一些问题，提出了准确定年的注意事项。  相似文献   

铅锌矿床Rb-Sr定年研究综   总被引：10，自引：0，他引：10  

李文博  黄智龙  许德如  陈进  许成  管涛 《大地构造与成矿学》2002,26(4):436-441

本文在总结Rb-Sr等时线定年的基本前提和矿床Rb-Sr等时线定年存在的问题的基础上,综述了铅锌矿床流体包裹体和闪锌矿Rb-Sr等时线定年的研究进展,同时对该定年方法存在的问题进行了简要评述。综合分析表明,Rb-Sr等时线定年(尤其是闪锌矿Rb-Sr等时线定年)为铅锌矿床较理想的直接定年方法,但该定年方法还存在许多理论和技术问题,有待深入研究;铅锌矿床Rb-Sr等时线定年应以深入细致的地质、地球化学研究为基础,定年过程中必须严慎对待样品采集、样品挑选、流体包裹体溶液提取和质谱分析等各个环节。  相似文献