U-Th-Pb dating of garnet based on LAICP-MS mapping technology: A case study of the Tonglvshan large-scale Cu -Fe-Au skarn depositSCIEI北大核心CSCD     

葛粲  汤笑伟  汪方跃  李修钰  孙贺  顾海欧  袁峰  郑辉 《岩石学报》2023,(10):2879-2894

矽卡岩矿床的年代学信息对研究矽卡岩矿床的矿床成因、演变过程、成矿规律和找矿勘查具有重要的指示意义。石榴子石是矽卡岩矿床中的常见矿物,它具有一定的U含量,但是由于其普通铅高以及铀分布不均一的原因,导致激光剥蚀电感耦合等离子体质谱仪(LA-ICP-MS)点分析获得年龄成功率不高。针对点分析定年遇到的深度分馏和剥蚀点选取、普通铅校正等问题,本文提出一种利用LA-ICP-MS面扫描分析数据的虚拟点构建技术,在Tera-Wasserburg(TW)图中实现普通铅校正来确定含普通铅石榴子石年龄。通过理论推导、数值模拟和实验分析研究发现,利用相关联的^(208)Pb、^(232)Th、^(238)U测量数据校正生成^(208)Pb_(c)/^(238)U指标并据此对TW图中的数据进行数据分组抽样构造虚拟测量点,可以有效地把面扫描测量数据转换为与点分析测量类似但放射母子比例展布更优的数据。利用此方法对长江中下游成矿带鄂东矿区铜绿山大型Cu-Fe-Au矽卡岩矿床石榴子石进行面扫描分析。仅使用15min的样品面扫描数据,在获得了微量元素含量分布的同时,也获得了同位素比值虚拟点,交点年龄为139.2±2.9Ma(MSWD=0.7,n=126),与前人矿床研究结果相一致,验证了此方法的可行性。利用LA-ICP-MS面扫描定年技术不仅可以获得样品元素含量的二维分布图,有利于对样品期次的筛选,剔除包裹体等异常数据;还可以避免点分析中深度分馏和繁复的选点流程及二次分析等步骤,在获得样品元素含量分布的同时获得矿物年龄,为当前矽卡岩型矿床相关的关键金属研究提供了更为便捷的方法。  相似文献   

云南易门狮子山铜矿床黄铜矿-斑铜矿Re-Os定年与S同位素组成     

王雷  丁金金  韩润生  任涛  李超  朱恩异  蒋宗和  黄亚虎 《地质学报》2021,95(3):837-851

易门狮子山铜矿床是康滇地区元古宙昆阳裂谷中的典型铜矿床之一,受狮子山背斜北西翼次级构造控制明显,矿石以脉状、浸染状、块状为主,少量呈层纹状。为厘定构造改造成矿时代,开展与石英、方解石脉共生的富黄铜矿、斑铜矿脉岩相学研究,挑选黄铜矿、斑铜矿单矿物,进行高精度的Re-Os同位素定年测试,获得了三组模式年龄,从早到晚依次为:(1)1749±18-1761±18Ma、(2)1358±14-1549±16Ma、(3)449.4±4.7Ma,其中获得第二组模式年龄的样品等时线年龄为1538±130Ma。据Re-Os同位素、硫同位素组成分析,落雪组中铜矿的成矿物质主要来源于地壳,部分来源于深源。结合矿区和区域构造-岩浆事件分析,认为矿区在古元古代发生了小规模岩浆热液成矿事件,形成了少量铜的硫化物;中元古代为矿区的主要成矿时期,该期成矿事件可能与刺穿构造形成时发生强烈的构造热事件作用有关;在早古生代早期也发生过小规模成矿事件,可能与加里东运动在该区的响应有关。  相似文献   

内蒙古架子山钼(银)矿床辉钼矿Re- Os同位素年龄及其地质意义     

王振亮  赵克强  杨剑洲  付燕刚  席明杰  李超  邓友茂  陆桂福 《地质学报》2021,95(12):3768-3777

本文通过对内蒙古架子山斑岩型钼(银)矿床7件辉钼矿样品的Re-Os同位素测定与分析,获得了辉钼矿的模式年龄介于143.1±2.1～147.2±2.4 Ma之间,加权平均年龄为145.8±1.4 Ma(MSWD=1.5),对应的等时线年龄为147.4±1.4 Ma(MSWD=1.5),表明架子山钼(银)矿床形成于晚侏罗世,属中国东部燕山期大规模钼成矿期成矿.架子山钼(银)矿床Re含量在37.62×10-6～401.34×10-6之间,平均值为121.28×10-6,表明架子山钼(银)矿床的成矿物质具有壳幔混源特征.  相似文献   

Low-rhenium molybdenite by metamorphism in northern Sweden: Recognition, genesis, and global implications   总被引：8，自引：0，他引：8  

Holly J. Stein   《Lithos》2006,87(3-4):300-327

Re–Os dating of molybdenite is an accurate means to date intrusions and intrusion-related ore deposits using the model age or isochron approach. But, molybdenite has a new niche in the greenschist- to granulite-facies metamorphic environment. Re–Os ages for metamorphic molybdenite may be used to construct regional metamorphic histories. Age significance and accuracy are established by analyzing multiple molybdenite separates extracted from single, petrographically-characterized molybdenite occurrences. In this study, twelve geologically distinct molybdenite-bearing samples from two small Mo districts in northern Sweden trace a 150 m.y. Paleoproterozoic Svecofennian metamorphic history from 1900 to 1750 Ma. These data reveal a little-known, widespread and protracted, Late Svecofennian anatexis in northern Sweden.The Kåtaberget Mo–(Cu, F) deposit is located in the Moskosel granite batholith north of the economically-renown Skellefte district. Four different molybdenite samples from outcrop at Kåtaberget indicate an intrusion age of 1895 ± 6 Ma with the formation of later pegmatite–aplite at 1875 ± 6 Ma. The Allebuoda (Björntjärn) and Munka Mo–(W) deposits in the Rappen district are represented by three outcrop and five drill core samples of molybdenite-bearing aplite–pegmatite–granite. These two deposits were previously described as intrusion-related Climax-type Mo mineralization. Re–Os ages for molybdenites from these deposits range from 1865 to 1750 Ma and, significantly, Re concentrations are markedly low, extending to the sub-ppm level. Age agreement within the deposits is conspicuously lacking, whereas, with one exception, age agreement within any single sample (geologic occurrence), as established by analysis of additional molybdenite separates, is very good. These data, together with fundamental geologic observations discussed in this paper, suggest that Mo–(W) mineralization in northern Sweden is not intrusion-related, but the local product of episodic melting of Archean–Paleoproterozoic supracrustal gneisses related to the Svecofennian orogeny. Petrographic traverses across the boundary between widespread, foliation-parallel units of aplitic to pegmatitic pink granite and hosting biotite gneiss directly capture the process of ore formation. Dehydration breakdown of zircon-rich biotite aligned with the foliation in the gneiss is accompanied by formation of new pristine, post-deformational biotite plus sulfides, oxides, hydrothermal zircon and fluorite, all associated with microcline-dominant leucosomes.This process has profound implication for the traditional leucogranite, intrusion-related genesis attributed to the broad classification of Mo–W–Sn–base and precious metal mineralization (e.g., South Mountain Batholith, Nova Scotia; Okiep, Namaqualand, South Africa; Mactung, Yukon; Pogo–Liese, Tintina, Alaska; Carajás and Goiás–Rio Tocantins, Brazil; New England Batholith, NSW, Australia; Bergslagen, Sweden; Nevoria, Western Australia; Alpeinerscharte, Austria; Erzgebirge, Germany; Sardinia–Corsica Batholith). In addition to biotite, metallogenic contributions (e.g., Mo, W, Sn, U, Bi, Cu, Pb, Zn, Fe, Ni, Co, Au, Ag, Te, As, Sb, REE) in various combinations may also be controlled by breakdown of amphibole. In effect, the trace element composition of dehydrating or recrystallizing components in a gneissic rock essentially defines the local and district metallogenic suite. In the absence of focusing structures (e.g., shear zones, sheeted vein development), this process will generally form small and disconnected subeconomic deposits with erratic and unpredictable grades. Low Re content in associated molybdenite is a key indicator for a subeconomic origin by local melting of biotite gneiss (Mo–W) or muscovite schist (Sn–W).  相似文献   

共炮检距二维弹性波地震剖面的偏移方法   总被引：1，自引：0，他引：1  

马在田 《地球物理学报》1995,38(Z1):1-10

在均匀各向同性介质的分界面上入射纵波时，除产生纵波反射Ｐ－Ｐ波外，还会产生转换横波的反射Ｐ－ＳＶ波。同样，当入射波为ＳＶ横波时，在分界面上会同时产生ＳＶ－ＳＶ反射波和ＳＶ－Ｐ反射转换波，对这种二维弹性波地震记录如何进行偏移是正在探讨的问题。为了能够处理实际地震数据，本文提出在共炮检距剖面上进行二维弹性波记录的偏移方法。具体做法是，首先用弹性波方程将两分量的地震记录分解为Ｐ－Ｐ（或ＳＶ－ＳＶ）波和Ｐ－ＳＶ（或ＳＶ－Ｐ）波，然后用我们已导出的适合于处理共炮检距剖面的叠前偏移方法对它们进行处理。用模拟数据进行的试验说明方法正确，效果良好。  相似文献   

Evidence of chromosomal damage in common eiders (Somateria mollissima) from the Baltic Sea     

Matson CW  Franson JC  Hollmén T  Kilpi M  Hario M  Flint PL  Bickham JW 《Marine pollution bulletin》2004,49(11-12):1066-1071

Common eiders nesting in the Baltic Sea are exposed to generally high levels of contaminants including potentially genotoxic polycyclic aromatic hydrocarbons and organochlorines. Blood samples were collected from eiders at eight sites in the Baltic Sea and two sites in the Beaufort Sea. DNA content variation was estimated using the flow cytometric method, and subsequently utilized as a biomarker of genetic damage. We observed no significant differences in genetic damage among populations within either the Baltic or Beaufort Seas. However, eider populations from the Baltic Sea had significantly elevated estimates of genetic damage compared to populations from the Beaufort Sea.  相似文献   

Molecular cloning and mRNA expression of cytochrome P4501A1 and 1A2 in the liver of common minke whales (Balaenoptera acutorostrata)     

Satoko Niimi  Michio X. Watanabe  Eun-Young Kim  Hisato Iwata  Genta Yasunaga  Yoshihiro Fujise  Shinsuke Tanabe 《Marine pollution bulletin》2005,51(8-12):784

This study presents full-length cDNA sequences of CYP1A1 and 1A2, in common minke whale (Balaenoptera acutorostrata) from the North Pacific. Both CYP1A1 and CYP1A2 cDNAs had an open reading frame of 516 amino acid residues, and predicted molecular masses were 58.3 kDa and 58.1 kDa, respectively. The deduced full-length amino acid sequence of CYP1A1 revealed higher identities with those of sheep (86%) and pig (87%), and that of CYP1A2 was most closely related to human (82%) and monkey CYP1A2 (82%) among species from which CYP1A2 has been isolated so far. Differences in certain conserved and functional amino acid residues of CYP1A1 and 1A2 between common minke whale and other mammalian species indicate the possibility of their specific metabolic function. Concentrations of organochlorine compounds (OCs) including PCBs and DDTs analyzed in common minke whale liver showed no significant correlation with hepatic mRNA expression levels of CYP1A1 and CYP1A2, indicating no induction of these enzymes by such OCs.  相似文献   

The geology and Re–Os geochronology of the Palaeoproterozoic Vaikijaur Cu–Au–(Mo) porphyry-style deposit in the Jokkmokk granitoid, northern Sweden     

Christina Lundmark  Holly Stein  Pär Weihed 《Mineralium Deposita》2005,40(4):396-408

The Vaikijaur Cu–Au–(Mo) deposit is located in the ca. 1.88 Ga calc-alkaline Jokkmokk granitoid near the Archaean–Proterozoic palaeoboundary within the Fennoscandian shield of northern Sweden. The Skellefte VMS district lies immediately to the south and the northern Norrbotten Fe-oxide–Cu–Au deposits to the north. The Vaikijaur deposit occupies an area of 2×3 km within the Jokkmokk granitoid and includes stockwork quartz-sulphide veinlets and disseminated chalcopyrite, pyrite, gold, molybdenite, magnetite, and pyrrhotite. Porphyritic mafic dykes were emplaced along fractures in a ring dyke pattern. The Jokkmokk granitoid, dykes, and the mineralized area are foliated, indicating that mineralization predated the main regional deformation. The mineralized area is characterized by strong potassic alteration. Phyllic and propylitic alteration zones are also present. A pyrite-rich inner core is surrounded by a concentric zone with pyrite, chalcopyrite, and gold. Molybdenite is distributed irregularly throughout the chalcopyrite zone. Geophysical data indicate a strongly conductive central zone in the mineralized area bordered by conductive and high magnetic zones. Five high precision Re–Os age determinations for three molybdenite occurrences from outcrop and drill core samples constrain the age of porphyry-style Cu–Au–(Mo) mineralization to between 1889±10 and 1868±6 Ma. A younger molybdenite is associated with a much later metamorphic event at about 1750 Ma. These data suggest that primary porphyry-style mineralization was associated with calc-alkaline magmatism within the Archaean–Proterozoic boundary zone at ca. 1.89–1.87 Ga.  相似文献   

Application of the Pt–Re–Os isotopic systems to mantle geochemistry and geochronology     

Richard W. Carlson   《Lithos》2005,82(3-4):249-272

The Re–Os system has now been applied to a wide variety of problems in the solid earth sciences. This review concentrates on applications of the Re–Os system to understanding the age and composition of the mantle and the role that various materials in the mantle play in generating surface magmas. The progress in understanding Re–Os systematics in natural materials has accompanied dramatic advances in the understanding of the geochemical behavior of Re and the platinum group elements. This group of elements and the two isotopic systems (Pt–Os and Re–Os) they contain provide a view of Earth processes that are controlled not by the silicate phases the make up most of the outer portion of Earth, but by sulfide, oxide and metal phases that constitute but a trace of the mantle and crust. These phases are sensitive to oxygen and sulfur fugacities in ways that silicates are not. Consequently, the Re–Os and Pt–Os systems provide a new view into the geochemical evolution of the solid Earth that is complementary to that obtained through the study of traditional radiometric systems that are based on lithophile elements.  相似文献   

中国大陆科学钻探100-2000m超高压变质岩普通Pb同位素地球化学初步研究——俯冲陆壳内脱耦的证据   总被引：1，自引：0，他引：1  

董锋李曙光  李秋立刘贻灿 陈福坤 《岩石学报》2006,22(7):1791-1798

本文首次对中国大陆科学钻探工程100～2000m榴辉岩中的绿辉石和片麻岩中的长石进行了普通Pb同位素研究。钻孔上部岩段（0-800m）样品放射成因Pb同位素含量比较高且变化幅度较小（^206Pb／^204Pb=16．81-17．29，^207Pb／^204Pb=15．37-15．45，^208Pb／^204Pb=37．20-37．66），说明其原岩的U／Pb和Th／Pb或者初始Pb同位素比值比较高。钻孔中部岩段（800-1600m）发育有韧性剪切带，相应的Pb同位素比值开始降低且有起伏（^206Pb／^204Pb=16．26-16．72，^207Pb／^204Pb=15．27～15．38，^208Pb／^204Pb=36．73～37．40）、钻孔下部岩段（800～1600m）样品放射成因Ph同位素含量低但变化幅度较小（^206Pb／^204Pb=16.05～16．46，^207Pb／^204Pb：15．22～15.29，^208Pb／^204Pb=36．68～37．48），说明其原岩的U／Pb和Th／Pb或者初始Ph同位素比值比较低。实测数据同模拟数据对比表明，钻孔上、下两岩段样品普通Ph同位素不同一方面是由于继承了原岩初始Pb同位素不同，另一方面是由它们的μ值不同所致。结合氧同位素研究，本文认为800m以上和1600m以下分属上地壳和中地壳．前者是从俯冲大陆岩石圈解耦的上地壳，在大陆岩石圈俯冲过程中，上部岩片同俯冲的大陆岩石圈发生挤离，率先沿着这一个挤离面逆冲折返至浅部。下岩片是随后从俯冲岩石圈解耦的中地壳岩片，并折返至浅部下伏在先期折返的上部岩片之下。考虑到中部岩段（800～1600m）既发育有韧性剪切带又具有异常低^18O峰值（Xiao et al．，2006），挤离面是在地壳内部晚元古代的断裂带及冷水活动通道基础上发育起来的。  相似文献