广西大厂拉么锌铜多金属矿床成岩成矿作用年代学研究

本文对广西大厂矿田拉么矿区内出露的酸性侵入岩和矿石进行了精细的年代学研究,分别获得龙箱盖含斑黑云母花岗岩锆石原位SHRIMP UPb和全岩RbSr等时线年龄为94±4Ma（95%可信度）和98.6±1.9Ma（95%可信度）,矽卡岩成矿期锌铜矿石中石英矿物RbSr等时线年龄为98.6±6Ma（95%可信度）。上述测定结果表明,拉么锌铜多金属矿床的成矿年龄与相关岩体的成岩年龄接近,均形成于早白垩世晚期。     

关于胶莱盆地东南缘基性火山熔岩喷发时代上限的讨论

首次对采自青岛即墨WN部两个深钻孔中新鲜玄武岩样品进行Rb-Sr同位素测年,测定年龄值为65.77±13.6Ma。认为该年龄值代表了胶莱盆地东南缘基性火山熔岩喷发的时代上限,对于整个胶莱盆地中基性火山岩的划分和对比具重要的年代学意义。     

康定杂岩Rb-Sr、Sm-Nd同位素系统及其意义

通过对康定—冕宁地区出露的英云闪长岩、黑云角闪斜长片麻岩、角闪变粒岩全岩及其中所分离出的角闪石、黑云母、斜长石、钾长石的Rb-Sr、Sm-Nd同位素的系统测定,结合岩石的锆石U-Pb年龄结果,确定这些变质杂岩由于经历了复杂的形成过程与变质历史,Rb-Sr、Sm-Nd同位素体系难以确定其结晶年龄。由单矿物与全岩Rb-Sr、Sm-Nd体系拟合的~700 M a的等时线年龄反映了角闪岩相-高角闪岩相的变质作用年龄。Sm-Nd同位素体系由于在变质作用过程中的部分开放性,很容易给出无意义的较老的混合年龄。康定杂岩结晶后并没有经历麻粒岩相变质作用,区域上所含的麻粒岩透镜体可能是新元古代(773~721 M a)期间由Rod in ia超大陆裂解产生的新生洋壳向扬子克拉通陆块俯冲消减过程的变质产物。俯冲到一定深度后,由于板片被拉断,软流圈上涌导致变质洋壳板片岩石、先前底侵变质的镁铁质岩石及扬子陆块长英质基底岩石发生部分熔融,以镁铁质岩石熔融产生的熔浆为主(>70%),与长英质基底岩石熔融产生的熔浆混合形成w(Na2O)/w(K2O)>1的TTG组合。     

福建行洛坑大型钨矿的地质特征、成矿时代及其找矿意义

行洛坑钨矿是目前福建最大也是武夷山成矿带最大的钨矿,已知储量主要分布于岩体内部,宜归属于斑岩型钨矿范畴。本文通过Re-Os法和Rb-Sr等时线法测定花岗岩体中辉钼矿的Re-Os等时线年龄为156.3±4.8Ma,石英脉中流体包裹体的Rb-Sr等时线年龄为147.5±2.9Ma,表明成矿作用与岩浆岩的形成基本同步,并延续了大约10Ma。因此,行洛坑钨矿虽然属于斑岩型钨钼矿但岩体以外的空间也可能找到石英脉钨矿,而整个武夷山成矿带中生代持续而复杂的成矿历史预示了其良好的找矿前景。     

湘南新田岭白钨矿床He,Ar同位素特征及Rb-Sr测年

新田岭白钨矿床是湘南W-Sn多金属矿集区中的一个大型矽卡岩型矿床,产于骑田岭岩体北接触带.本文对矽卡岩矿石中1件黄铁矿样品进行了流体包裹体He、Ar同位素测定,获得3He/4He值为4.08 Ra,40Ar/36Ar为342,反映了在矽卡岩矿床的成矿流体中亦有地幔流体的显著参与;运用石英Rb-Sr法获得成矿等时线年龄为(157.4±3.2)Ma(2σ)(MSWD=1.6),87Sr/86Sr初始值为0.71044±0.00012,该年龄值与柿竹园超大型钨多金属矿床及芙蓉大型锡矿等的成矿年龄在测试误差范围内基本一致,表明中侏罗世是湘南地区钨锡成矿的高峰期.     

江西金山金矿含金黄铁矿的Rb-Sr年龄

前人对江西金山金矿的成矿时代有许多不同的认识,笔者通过对江西金山蚀变岩型矿石中的含金黄铁矿Rb-Sr年龄的测定得出,含金黄铁矿的Rb-Sr等时线年龄为(838±110)Ma,initial87Sr/86Sr=0.7045±0.0020。由此可以推测晋宁期是蚀变岩型金矿体形成的主要时期。黄铁矿Rb-Sr所得的Sr同位素初始比(87Sr/86Sr)i小于陆源硅酸盐的值(0.720),而与玄武岩的值(0.704)接近,结合前人有关的同位素及稀土、微量元素研究,笔者认为金山金矿变质岩型矿体的成矿物质源于变质围岩,成矿流体为来源于深部的变质水。     

Paleoproterozoic accretion in the Northeast Siberian craton: Isotopic dating of the Anabar collision system

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.     

Chemical, Isotopic, and Fluid Inclusion Evidence for the Hydrothermal Alteration of the Footwall Rocks of the BIF-Hosted Iron Ore Deposits in the Hamersley District, Western Australia

Abstract. The petrography, chemical, fluid inclusion and isotope analyses (O, Rb-Sr) were conducted for the shale samples of the Mount McRae Shale collected from the Tom Price, Newman, and Paraburdoo mines in the Hamersley Basin, Western Australia. The Mount McRae Shale at these mines occurs as a footwall unit of the secondary, hematite-rich iron ores derived from the Brockman Iron Formation, one of the largest banded iron formations (BIFs) in the world. Unusually low contents of Na, Ca, and Sr in the shales suggest that these elements were leached away from the shale after deposition. The δ¹⁸O (SMOW) values fall in the range of + 15.0 to +17.9 per mil and show the positive correlation with calculated quartz/sericite ratios of the shale samples. This suggests that the oxygen isotopic compositions of shale samples were homogenized and equilibrated by postdepositional event. The pyrite nodules hosted by shales are often rimmed by thin layers of silica of varying crystallinity. Fluid inclusions in quartz crystals rimming a pyrite nodule show homogenization temperatures ranging from 100 to 240C for 47 inclusions and salinities ranging from 0.4 to 12.3 wt% NaCl equivalent for 18 inclusions. These fluid inclusion data give direct evidence for the hydrothermal activity and are comparable to those of the vein quartz collected from the BIF-derived secondary iron ores (Taylor et al, 2001). The Rb-Sr age for the Mount McRae Shale is 1,952 ± 289 Ma and at least 200 million years younger than the depositional age of the Brockman Iron Formation of ∼ 2.5 Ga in age. All the data obtained in this study are consistent with the suggestion that high temperature hydrothermal fluids were responsible for both the secondary iron ore formation and the alteration of the Mount McRae Shale.     

山西铝土矿Rb-Sr同位素定年

采用Rb Sr全岩与粘土矿物等时线年龄方法测得山西五台剖面 (RS0 1) ,临县剖面 (RS0 2 )和孝义剖面 (RS0 3)的 3个含矿粘土岩的Rb Sr同位素年龄分别为 :316 .9± 1.2Ma ,87Sr/86Sr为 0 .710 5 4± 14 ;315 .5± 1.3Ma ,87Sr/86Sr为 0 .710 86±18;317.3± 1.1Ma ,87Sr/86Sr为 0 .710 5 0± 14。它们代表了铝土矿和含矿系列成矿的同位素年龄 ,相当于晚石炭世早期     

硅岩的Rb-Sr同位素组成特点及其地质意义

通过对扬子地台和东昆仑山地区的不同时代、不同成因、成分上差异较大的硅岩Rb-Sr同位素组成的对比研究，探讨其物源和形成环境，利用所测Rb-Sr等时线年龄，有效的解决硅岩的地层年代，开创硅岩测年的应用前景。