中甸普朗斑岩型铜矿床围岩蚀变初步研究

普朗斑岩型铜矿床是近年发现的一个重要铜矿床,通过大量的野外地质资料收集和室内综合分析研究,结合钻探、物探、化探和遥感技术应用的成果,初步认为普朗印支期斑岩铜矿床热液蚀变是经过多期次、多阶段构造-热液事件形成的,具有由中心向外依次为硅化核、硅化、钾化带-绢英岩化带-青磐岩化带-角岩化带的面型蚀变特征。其中硅化、钾化、绢英岩化蚀变带与铜矿关系密切。蚀变作用既影响岩(矿)石的结构、构造,又导致矿石中主要氧化物含量和Cu品位的变化。矿化与蚀变引起的物探、化探和遥感异常有较好的关联性,异常是找矿与勘查的直接标志和指导工程布置的依据,对于在中甸地区寻找与勘查同类型矿床有重要意义。     

滇西北普朗斑岩铜矿床成矿时代及其意义

普朗斑岩铜矿在中国斑岩铜矿床中有其特殊性,无论对中甸岛弧带的基础地质还是矿产资源评价预测的研究,都具有重要意义。然而,该斑岩铜矿床无确切的年代学数据。通过作辉钼矿Re-Os年龄和单矿物K-Ar年龄测定,首次确定了普朗斑岩铜矿床内具有钾硅酸盐化的黑云石英二长斑岩成矿作用的活动时间为(235.4±2.4)Ma～(221.5±2.0)Ma,石英-辉钼矿阶段的辉钼矿Re-Os年龄大致为(213±3.8)Ma,两者十分相近。表明普朗斑岩铜矿床的成矿作用是在印支期完成的。主矿体钾长石K-Ar年龄显示热液活动持续到(182.5±1.8)Ma左右,说明与斑岩铜矿有关的热液系统寿命可达40Ma之久。这种长寿命的热液系统是高品位大规模的斑岩铜矿形成的必要条件之一。     

广州地区瘦狗岭断裂40Ar-39Ar同位素年龄及其地质意义

采用40Ar/39Ar坪年龄和40Ar/36Ar-39Ar/36Ar等时线法对广州瘦狗岭断裂中的黑云母作了同位素年龄测定,获得(86.36～216.91)×106a的区间年龄.其中,(216.91±4.64)×106a为萝岗花岗岩类组合的形成年龄,40Ar/36Ar-39Ar/36Ar等时线年龄(172.20±0.52)×106a为韧性剪切带形成年龄,(86.36±0.91)×106、(119.73±1.02)×106和(145.61±1.04)×106a为后期热事件叠加年龄;从而说明,本区燕山早期构造作用以逆冲挤压为主.     

40Ar-39Ar同位素定年方法研究进展

^40Ar-^39Ar同位素定年法是由K-Ar法发展而来,通过将39K利用快中子辐照衰变成^39Ar,测量40Ar^＊/^39Ar来获得年龄值.经过长期发展,该方法的测试技术逐渐成熟,其中气体提取发展为常规阶段升温法、激光显微探针法以及真空压碎流体包裹体法;气体纯化主要有冷阱去除法、钛泵吸附法、锆铝泵吸附法;气体测试的质谱仪也在灵敏度、分辨率、背景值等技术指标上有很大提高.^40Ar-^39Ar同位素定年法在石油、固体矿产等方面应用广泛,尤其在油气成藏时间、成岩成矿作用时间的热年代学研究等领域.     

中甸火山-岩浆弧燕山期热林复式岩体演化 与Ar-Ar 定年及铜钼矿化

产于中甸印支期火山一岩浆弧北东缘的燕山期热林复式岩体,从早至晚边部到中部划分出主期由细粒似斑状二长花岗岩→中粒似斑状二长花岗岩和边部补充期二长花岗斑岩5个侵入体组成的同源岩浆细粒→中粒→斑状结构演化系列.岩体岩石化学、稀土和微量元素总体反映为同熔型花岗岩特征.在复式岩体Ⅱ号侵入体中粒似斑状二长花岗岩中获黑云母Ar-Ar同位素等时年龄81.7±1.1Ma,坪年龄82.01±0.86 Ma,属燕山晚期侵入体.铜钼矿主要产于晚期侵入体中,边部细粒花岗岩和角岩内带具有细脉状黄铜矿、团块状辉钼矿化;中部发生二长花岗(斑)岩热液蚀变充填交代辉钼矿化--辉钼矿石英细脉、中粗晶浸染状;以及沿裂隙发育岩浆期后含矿热液充填交代辉钼矿化,构成燕山期花岗斑岩铜钼成矿亚系列.成因类型:蚀变花岗斑岩、石英脉型和角岩型3种,指示了燕山期二长花岗斑岩类具有较好的铜钼找矿潜力.     

藏北祖尔肯乌拉山地区新生代火山岩40Ar-39Ar同位素定年及其意义

通过对藏北祖尔肯乌拉山地区大面积分布的新生代火山岩的^40Ar-^39Ar同位素测年结果分析表明,火山岩^40Ar-^39Ar同位素年龄介于45Ma～39Ma之间,集中于40Ma左右,属始新世。火山岩^40Ar-^39Ar同位素年龄的精确限定,不仅为该区生物化石缺乏的新生代陆相红层沉积时代上限提供了同位素年代学依据,而且为藏北EMⅡ型富集地幔形成时限提供了同位素年代学的约束。     

滇西北中甸普朗斑岩铜矿床地球化学与成矿机理初探

普朗斑岩铜矿是一个典型的与洋壳俯冲相关的大型乃至超大型矿床,通过对矿区代表性含矿斑岩与无/弱矿化斑岩的稀土元素特征对比、硫同位素示踪等方面的研究,表明矿石随Cu品位的增高,稀土总量(∑REE)和稀土分馏参数〔(LREE/HREE)、(La/Yb)N及(La/Yb)N、(Gd/Yb)N〕呈连续降低趋势,负铕异常一般显示为逐渐增强的趋势,但在发育有强烈的晚期钾长石脉的情况下,出现反弹减弱特征。硫化物(黄铜矿、黄铁矿和辉钼矿)的δ34SCDT变化范围为-2.23‰～3.75‰,基本呈塔式分布特征,主要为深源岩浆硫。     

滇西北普朗斑岩铜矿锆石离子探针U-Pb年龄: 成矿时限及地质意义

应用高精度离子探针锆石U-Pb测年方法,获得普朗斑岩铜矿床中3件矿化石英二长斑岩的锆石年龄分别为228±3Ma、226.3±2.8Ma、226±3Ma。锆石形态和铀钍参数均属典型的岩浆锆石特征,年龄值在误差范围内近似一致,表明形成矿化斑岩的中酸性岩浆从岩浆房快速上升侵位。结合前人已发表的矿化斑岩的黑云母Ar-Ar坪年龄及辉钼矿Re-Os同位素年龄等数据,推测普朗斑岩铜矿的岩浆—热液系统从岩浆侵入至矿化阶段的持续时间可能长达10Ma以上,主成矿期约为216~214Ma。从岩浆房分异出的富含成矿物质和挥发份的岩浆流体在相对较晚阶段对普朗复式岩体发生了强烈的蚀变作用并可能进一步萃取了岩体中的成矿物质。     

广东东镇岩体微区^40Ar／^39Ar年龄及其意义

采用激光显微探针＾４０Ａｒ／＾３９Ａｒ测年技术（简称微区＾４０Ａｒ／＾３９Ａｒ法）对广东云开地区东镇岩体含眼球体的片麻状花岗质岩石中单矿物作了同位素年龄测定，获得眼球体内核中的巨晶状钾长石年龄（４１９．４０±４．３７）×１０＾６ａ。眼球体角缘中重结晶微粒状钾长石年龄（２７２．６３±３．１３）×１０＾６ａ，眼球体外壳中的强应变长条纹黑云母年龄（１７７．８４±２．２９）×１０＾ａ。暗色条带中的弱应变板     

西藏纳如松多隐爆角砾岩型铅锌矿床绢云母Ar-Ar定年及其地质意义

纳如松多铅锌矿床位于拉萨地块中部隆格尔-工布江达断隆带中段,为冈底斯铜矿带北侧铅锌银多金属成矿带的典型矿床之一。纳如松多铅锌矿床以发育隐爆角砾岩型和矽卡岩型铅锌矿化为特征。利用40Ar-39Ar同位素测年方法对纳如松多东矿段隐爆角砾岩型主矿体成矿阶段形成的绢云母进行了年龄测定,获得绢云母Ar-Ar坪年龄为(57.81±0.66)Ma,对应的正、反等时线年龄分别为(57.90±1.70)Ma、(57.70±0.77)Ma。所测坪年龄与正反等时线年龄具有很好的一致性,可以代表隐爆角砾岩型铅锌矿体的形成年龄。结合区域地质构造背景,纳如松多隐爆角砾岩型铅锌矿床形成于印度-亚洲大陆主碰撞时期。     

云开群硅质岩的40Ar/39Ar年龄及其地质意义

粤西云开群浅变地层年代的确定对于研究华南地壳演化有重要意义。以往的同位素年龄值多测自其中的顺层火成岩，故对其他质意义有不同的理解。本文首次测得了云开群中硅质岩的40Ar/39Ar年龄，从而提供了云开群的沉积年代。     

新疆甘肃交界红柳河蛇绿岩中伸展构造与古洋盆演化过程

红柳河蛇绿岩中保存了大量伸展特征构造，如堆晶辉长岩层中发育丰富的辉长质糜棱面理、伸展褶劈理、小型韧性低角度正断层、韧-脆性共轭正断层和脆性正断层等伸展变形构造。蛇绿岩中伸展变形构造经历了完整的变形序列：从韧性变形、经韧脆性变形到脆性变形。构造几何学关系表明这些构造形成于红柳河古洋盆闭合之前洋壳扩张过程中。^40Ar／^39Ar年代学的研究确定了红柳河古洋盆演化的过程：洋盆扩张发育在462Ma之前，并在412Ma前闭合。     

New Discovery of the Early Cretaceous Volcanic Rocks on the Barton Peninsula, King George Island,Antarctica and Its Geological Significance

Ages determined with the 40Ar/39Ar isotopic system affirms the Early Cretaceous volcanic activity in the Barton Peninsula, King George Island, Antarctica. Two specimens of basaltic andesite collected from the lowermost volcanic sequence of the peninsula were irradiated and analyzed in different experiments, yielding an identical age spectrum, and two magmatic thermal events of the Early Cretaceous (120.4± 1.6 Ma, 119± 1 Ma) and Early Tertiary (53.1± 1.5 Ma, 52± 1 Ma) are distinguished. The former is interpreted to represent the primary cooling age of basaltic andesite, whereas the latter is the thermal reset age caused by the intrusion of granitic pluton. These new ages clearly indicate that volcanism was active during the Early Cretaceous on the Barton Peninsula and that intensive hydrothermal alteration and mineralization of Mesozoic volcanic rocks resulted from Tertiary magmatism.     

桐柏杂岩的中生代隆升机制及其与南阳盆地沉降的耦合关系

桐柏山位于我国的中央造山带东部,走向北西—南东,南北跨越鄂豫两省,向西北倾没于南阳盆地之下,向南东过渡到大别山。山体由一套变质杂岩组成,南北两侧为含榴辉岩的高压变质地体,其构造就位过程一直为广大地质学家所关注。我们通过野外地质考察发现,该山体在地貌上呈北陡南缓的格局,表明它在演化的晚期经历过一次向南的掀斜运动。殷店和桐柏韧性剪切带构成山体的南北边界。前者倾向南,呈右行剪切,后者倾向北,呈左行剪切。殷店断裂中的糜棱岩产状很稳定,一直延伸到桐柏山主峰——太白顶(1 140 m)。其下部为桐柏杂岩体,后者的产状虽然复杂,但其中的拉伸线理的产状却稳定,走向北西—南东,向北西倾伏。按此产状追索,它们也应倾没于南阳盆地之下。通过构造恢复,可以推断在掀斜运动发生之前,殷店和桐柏韧性断裂应连为一体,构成一个向北西倾伏的低角度正断层,本文称之为太白顶拆离断层。基于对桐柏杂岩的运动学和显微构造学研究,可以推断桐柏杂岩原来位于东秦岭之下,是中下地壳的组成部分,由于中生代华北和扬子两板块的碰撞和持续的陆内汇聚作用而造成南东侧向挤出,它们作为异地地体从原地地体—超高压变质岩之下隆升到地表,太白顶拆离构造的功能与藏南拆离系一样,构成桐柏杂岩隆升顶部的滑脱面。~(40)Ar/~(39)Ar年代学研究结果表明,桐柏山侧向挤出隆升造山事件发生在晚白垩纪早期(102～85 Ma)。南阳盆地形成于桐柏山的西侧,是一个东断西超的半地堑盆地,其沉积作用始于早白垩世,大规模沉陷发生在晚白垩世,这与桐柏山的隆升是同时的,反映出沉积和构造隆升是耦合的。     

Geochronology of the Dong Tso Ophiolite and the Tectonic Environment

The wedge shaped Dong Tso ophiolitic block is distributed near the transition point from the western to the middle sub-belt of the Bangong-Nujiang suture zone.The ophiolite is characterized by well-developed cumulate rocks that are mainly composed of cumulate and massive gabbros.In the cumulate gabbros,the adcumulate amphiboles are distributed extensively around the plagioclase and residual pyroxene grains; hence,the rocks are named adcumulate amphibole-gabbro.In this study,the formation age of the ophiolite has been estimated to be 166 ± 4 million years （Ma） by the sensitive high-resolution ion microprobe （SHRIMP） Ⅱ U-Pb isotopic analysis of the zircons from the adcumulate amphibole-gabbro; the 40Ar/39Ar plateau age was estimated to be 148.19 ± 1.53 Ma,which should represent the emplacement time of the ophiolite,by isotopic dating of the pure amphibole mineral from the amphibole-schist.Two different suits of volcanic lavas have been recognized in this work.The purple colored pillow basalts have high TiO2 and P2O5 contents,and are rich in light rare earth elements （LREEs）,large-ion lithospheric elements （LILEs） and high-field-strength elements （HFSEs）,the characteristics that are the typical of the oceanic island basalt （OIB）.On the other hand,other massive basaltic andesites of celadon color are poor in MgO; rich in Fe2O3,LREEs,LILEs,and HFSEs; and especially characterized by negative Nb and Ta anomalies,the properties that establish the andesites as continental arc volcanic rocks.It is concluded that hotspots had developed in the old Dong Tso basin,the oceanic basin that had been developing from middle Jurassic （166 Ma） or even before and emplaced northward in late Jurassic （about 148 Ma）.     

滇西南那邦变质基性岩两期变质作用的40Ar/39Ar年代学研究

中缅边界那邦变质基性岩出露于东缅著名的 Mogok带的东缘。那邦基性麻粒岩经历了早期麻粒岩相、晚期角闪岩相的两期变质作用的改造。早期变质作用的矿物石榴石和单斜辉石的 40 Ar/ 39Ar激光微区等时线年龄是 74.44± 1.44 Ma;石榴石和单斜辉石的 40 Ar/ 39Ar年龄谱图和等时线年龄均显示两组年龄 :74～ 76 Ma和 2 3～ 2 4Ma。晚期变质作用矿物角闪石的K- Ar法得出 2 3Ma,角闪石和斜长石的 40 Ar/ 39Ar年龄谱图和等时线年龄均显示 2 3～ 2 4Ma的变质年龄。综合这些结果 ,可以确定那邦基性麻粒岩的早期麻粒岩相变质作用的年龄是 74～ 77Ma,可能与新特提斯洋壳俯冲事件有关 ;晚期角闪岩相变质作用的年龄是 2 3～ 2 4Ma,与区内喜山期以来陆内块体响应两大陆会聚作用发生的大型走滑事件有关。那邦基性麻粒岩是世界上最年轻的麻粒岩相岩石之一 ,而且 ,两期变质作用年龄的确定对揭示区内与变质作用相关的地质事件具有重要意义。     

西藏阿里地区冈底斯花岗岩体的热年代学特征及其构造意义

冈底斯花岗岩带是沿雅鲁藏布江北侧近东西向展布的一条长约2 500 km、宽100～300 km的巨型岩浆岩带。在阿里冈底斯山主峰岗仁波齐峰附近,冈底斯花岗岩体受到多期断裂活动的影响,特别受喜马拉雅大反向断裂和喀喇昆仑断裂活动的改造,造成断裂和岩体的关系出现很多复杂的情况,一些研究者把在北阿伊拉日居山分布的32～25 Ma的花岗岩作为喀喇昆仑断裂活动引起的同构造花岗岩,并把此年龄段归结为断层活动年龄,从而引起了极大的争论。本文的锆石U-Pb年龄指示了岗仁波齐峰地区的冈底斯花岗岩是由110 Ma、60 Ma和50 Ma的3期花岗岩组成,而韧性剪切带内的锆石年龄与附近未变形岩石内的锆石年龄一致,表明锆石的形态并未受到断裂活动的影响。韧性剪切带内云母的氩氩年龄为12 Ma左右,而周围未变形花岗岩的云母氩氩年龄在60～50 Ma左右,由此表明喀喇昆仑断裂在岗仁波齐峰地区是12 Ma开始活动的。由于研究区内韧性剪切带中的变形花岗岩并没有记录32～25 Ma这期热事件,由此排除了断裂在狮泉河-门士一线是32～25 Ma开始活动的可能性。     

侏罗系——白垩系界线年代研究

本文采用界线层型标定地层界线的方法，以河北滦平县井上－大店子和大北沟两界线层型剖面的生物地层研究结果，确定我国陆相侏罗系－白垩系界线在大北沟组与大店子组之间，对滦平县热河群下部及其下伏岩层中的火山岩层进行４０Ａｒ／３９Ａｒ法年代学研究，并推定侏罗系－白垩系界线年龄为１４０±１Ｍａ。     

Petrogenesis of oligocene plutonic rocks in western Anatolia (NW Turkey): Insights from mineral and rock chemistry,Sr-Nd isotopes,and U-Pb,Ar-Ar and (U-Th)/He geochronology

Northwestern Anatolia is characterized by voluminous Paleozoic to Cenozoic granitoid bodies with varying compositions. Most of them are composite plutons emplaced into western Anatolia orogenic crust during the Eocene, Oligocene and Miocene along the İzmir-Ankara-Erzincan suture zone. This paper reports systematic good quality mineral and bulk-rock chemistry, Sr-Nd isotope data, honblend Ar-Ar, zircon U-Pb and first apatite (U-Th)/He (AHe) ages to reveal possible source compositions of the Evciler and Eybek granitoids and petrogenetic/geodynamic processes involved during their genesis, and thermochronology of Oligocene magmatism in the NW Anatolia. The Evciler and Eybek granitoids are mainly granodiorite and composed of K-feldspar (usually orthoclase and rarely microcline), plagioclase (albite, oligoclase), hornblende, biotite, quartz and accessory minerals (e.g., titanite, zircon, apatite, opaque), and secondary minerals such as chlorite, sericite and clay minerals. Estimated temperature-pressure conditions are 690–770 ° C at 1.6–2.7 kbar for the Evciler granitoid and 690–760 ° C at 3.2–4.01 kbar for the Eybek granitoid. These two granitoids enriched in LILEs (e.g., U, Th, Rb, and K), LREEs and Pb, and depleted in HREEs (e.g., Nb, Ti) and Sr, Ba and P relative to LILEs, and display small negative Eu anomalies. They belong to calc-alkaline, high-K calc-alkaline and minor shoshonite series, and display metaluminous and I-type character. Their REE patterns show a large fractionation between LREE and HREE ((La/Yb)N = 4.6–21.4) and a small negative Eu anomaly (Eu* = 0.2–0.3). The Evciler granitoid has homogeneous ⁸⁷Sr/⁸⁶Sr = 0.7060−0.7063 and ¹⁴³Nd/¹⁴⁴Nd = 0.51259−0.51262, and the Eybek granitoid has ⁸⁷Sr/⁸⁶Sr = 0.7060−0.7080 and ¹⁴³Nd/¹⁴⁴Nd = 0.51243−0.51263. New precise ⁴⁰Ar/³⁹Ar age data of hornblende and ²⁰⁶Pb–²³⁸U ages of zircons and (U-Th)/He ages of apatites from the plutons allow a more accurate temporal reconstruction of the Cenozoic magmatism of the western Anatolia. ⁴⁰Ar/³⁹Ar dating of hornblendes from the Evciler and Eybek granitoids gave plateau ages of between ca. 28 Ma and 25 Ma. Laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) ²⁰⁶Pb-²³⁸Pb ages of euhdral magmatic zircons from the samples of these granitoids yield between ca. 28 and 26 Ma. The new high-temperature age constraints indicate Oligocene emplacement ages for the two intrusive bodies. The closeness of the zircon U-Pb and the hornblende Ar-Ar ages show that they experienced quick post-crystallization cooling. However, the significant difference between the apatite (U-Th)/He ages of 19.8 Ma and 7.6 Ma obtained on the Evciler and Eybek granitoids warns that in the post-Oligocene times the two structural blocks had different exhumation histories.