Thermochronology for the Granitic Pluton Related to Lead-Zinc Mineralization in Tsushima, Japan

Abstract: K–Ar datings and oxygen isotope analyses revealed a cooling history of the Uchiyama granitic pluton, which is genetically related to the Pb-Zn deposits (Taishu mine) in the Tsushima Islands, Japan. The pluton intrudes into the Paleogene Taishu Group to form the biotite-hornfels zone, while the Taishu vein-type Pb–Zn deposits occur in fissures developed in the non-hornfels zone about 1 to 3 km westward from the contact. Amphibole and biotite K-Ar ages of the pluton have a wide range from 19 to 13 Ma. Oxygen isotopes of the biotite and coexisting quartz grains indicate that isotopic exchange reactions have occurred under subsolidus conditions, and that the K-Ar ages are affected by various cooling rates in the pluton. The mineralization age of the Taishu ore deposits is obtained for the first time to be 15.40.8 Ma by a K-Ar age of 2 M ₁–muscovite in a calcite–quartz–muscovite–chlorite veinlet of the Shintomi orebody. Whole rock K-Ar ages of biotite-hornfels near the pluton represent similar ages to the ore deposits. Using blocking temperature calculated from reported diffusivity for argon, the pluton was cooled from 560 to 350C in the period of 17 to 14 Ma. The vein formation took place after the time when temperature in wall rocks of the pluton had dropped below the brittle-plastic transition (about 400C). These results imply that the cooling of the pluton has caused injection of magmatic fluids into meteoric hydrothermal systems, and the Pb-Zn mineralization has occurred due to this mixing at the age of about 15 Ma.     

激光质谱测定南极乔治王岛北海岸A635玄武岩微区~(40)Ar-~(39)Ar的等时年龄

采用连续激光直接对岩石光片样品微区熔样，以高灵敏度、高精确度的质谱计测试，对南极乔治王岛玄武岩样品进行（４０）Ａｒ－（３９）Ａｒ法定年，取得了成功。样品置反应堆中心Ｅ－５孔道，以１．８×１０（１８）ｎ／ｃｍ２的快中子总通量照射，时间为５０ｈ，放射性冷却后进行测定。样品的加热源为自行设计的Ｎｄ：ＹＡＧ固体激光器，以Ｈｅ－Ｎｅ准激光器导光。测定中对４个２５０μｍ直径的微区分别在１５００℃高温熔融，经Ｚｒ－Ａｌ泵纯化的气体用ＭＭ１２００质谱计测量氩同位素各峰值。经计算得到该样品的等时年龄为５２．４±１．１Ｍａ，远远低于江个点的视年龄值，而（（４０）Ａｒ／（３６）Ａｒ）＞＞２９５．５。这不仅证明该样品含有过剩氩，同时也证明了由Ｋ－Ａｒ稀释法得到的偏高年龄值亦是样品中存在过剩氩造成的。激光微区等时年龄的获得进一步厘定了南极乔治王岛北海岸火山岩时代为第三纪，同时证明了我们建立的激光质谱微区、微粒熔样和测定技术是可行的和成功的。     

“A world in a grain of sand”: towards a reconceptualisation of geographical scale

Difficulties in relating local scale change to broader dynamics of social and economic restructuring continue to be reflected in much geographical research. This paper argues that inadequate conceptualisations of geographical scale restrict the relevance of much research to the agenda of an applied peoples' geography. A framework which conceptualises geographical scale as dialectically and internally related to the totality of social relations, is proposed and discussed with examples from remote mining regions in Australia.     

浙江省陈蔡群的^40Ar—^39Ar年龄与变质年代

本文对陈蔡群变质岩进行了４０Ａｒ－３９Ａｒ年龄测定。其中在诸暨陈蔡测得的４１５．１Ｍａ的坪年龄代表了主变质晚期的冷却年代。采自义乌尚阳的样品受燕山期火山活动影响有明显的氩丢失，与主变质有关的年龄亦明显降低，仅３１５．３Ｍａ。在龙泉东书获得的年龄谱和当地广泛发育的混合岩化作用有关，２７６．９Ｍａ的坪年龄为这次热事件的冷却年代。根据对现有年代资料的讨论，可以认为不同衰变体系记录了陈蔡群主变质事件的演化。Ｒｂ－Ｓｒ体系在变质早中期实现均匀化，年龄值为５５２．４～６６０．６Ｍａ。锆石、磷灰石在变质高峰期形成的铅丢失年龄为５０８，４～５７８Ｍａ。上述资料表明陈蔡群主变质年代属加里东期。     

海绿石 K-Ar、40Ar/39Ar 年代学研究

海绿石是与沉积岩同时形成的高钾层状硅酸盐自生矿物，其 K-Ar、40Ar/39Ar 年龄存在失真现象。笔者认为，引起年龄失真的主要原因是由于该矿物结构中含有可膨胀层。通过测量可膨胀层含量及中子活化过程中39Ar的丢失率，使可对海绿石常规 K-Ar、40Ar/39Ar 年龄进行校正，得到其年龄校正公式。     

Volcanic history of Mount Sidley,a major alkaline volcano in Marie Byrd Land,Antarctica

Mount Sidley is a complex, polygenetic stratovolcano composed primarily of phonolitic and trachytic lavas and subordinate pyroclastic lithologies at the southern extremity of the Executive Committee Range, a linear chain of volcanoes in central Marie Byrd Land, Antarctica. Detailed field investigation coupled with 14 high precision ⁴⁰Ar/³⁹Ar age determinations reveal a 1.5 million year life span between 5.7 and 4.2 Ma in which three major phonolitic central vent edifices (Byrd, Weiss and Sidley volcanoes) and their calderas were developed (5.7–4.8 Ma). This was followed (4.6–4.5 Ma) by the eruption of trachytic magmas from multiple vent localities further south, and then by small volume benmoreite-mugearite lavas and tephras around 4.4–4.3 Ma at the southern end of Mount Sidley. The final phase of activity was the eruption of basanite cones at approximately 4.2 Ma. The southward migration of volcanic activity was accompanied by distinct changes in magma composition and is best explained by the sequential release of magmas stored within an intricate system of conduits and chambers in the crust by tectonically driven (magma assisted?) fracture propagation. The style of volcanic migration at Mount Sidley is emulated on a larger scale by other volcanoes in the Executive Committee Range, in which progressive southward displacement of volcanic activity corresponds with significant petrological variations between major centers.     

^40Ar／^39Ar定年中干扰同位素的质谱校正与低温分离技术

将光谱纯的CaF_2和优级纯的K_2SO_4同样品一起在反应堆中照射,用MM-1200质谱计分别对其熔融释放的气体进行测定,得到干扰同位素校正因子: C_2=(~(36)Ar/~(37)Ar)_(Ca)=(2.40±0.24)×10~(-4) C_4=(~(39)Ar/~(37)Ar)_(Ca)=(8.06±0.10)×10~(-4) C_3=(~(40)Ar/~(39)Ar)_K=(3.18～6.86)×10~(-3) 将被照射过的含Cl样品释放的Ar和Cl混合气体,通入被冷却到-90℃的弯管,Cl被冷冻在弯管内,Ar气体通过弯管再经净化送入质谱计分析。实验证明,该法可有效的将~(36)Cl从样品气体中分离出去,消除了~(36)Cl的干扰。     

Die permische Differentiation und die alpidische Metamorphose des Granitgneises von Wolfsberg,Koralpe, SE-Ostalpen,mit Rb−Sr- und K−Ar-Isotopenbestimmungen

Zusammenfassung Der Granitgneis von Wolfsberg, Koralpe, Kärnten, konnte mit einer Rb–Sr-Gesamtgesteins-isochrone als jungpermisch mit 258±11 M.J. bestimmt werden, mit einem initialen 87 Sr/86 Sr-Verhältnis von 0,7046±0,0028. Die alpidische Metamorphose wird durch Mineralabkühlalter an Hellglimmern und Biotiten eindeutig belegt: Hellglimmer: Rb–Sr: 80 und 79±3 M. J.; K–Ar: 78 und 75±3 M.J. Biotite: Rb–Sr: 77–73±3 M.J.; K–Ar: 80±3 M. J. (5, bzw. 3 Proben).Von den Hellglimmern wird zum ersten Mal für Österreich eine reine 3-T-Modifikation beschrieben. Die mehrphasige Geschichte des Granitgneises und seine tektonische Position werden diskutiert.Mit 5 Abbildungen     

地热规模化开发断层滑动概率评估——以雄安新区深部岩溶热储为例

雄安新区地热资源丰富，具有广阔的规模化开发利用前景，对于实现"绿色雄安"具有重要意义。许多学者的研究集中在地质结构探测、地热资源量评价、地壳稳定性等方面，关于深部岩溶热储规模化开发可能引起的断层滑动研究薄弱。本文在地热地质综合调查的基础上，基于地质力学理论，采用蒙特卡罗随机模拟方法，评价雄安新区主要断层特征（走向、倾角、滑动摩擦系数等）、地应力分布（孔隙压力、最大/最小/垂直主应力大小及方向等），量化雄安新区天然断层在规模化开发利用情况下的激活可能性，结果显示已探明断层在天然、规模化回灌和水力压裂条件下的最大滑动趋势分别为0.26、0.27和0.40，地热开发不会引起断层激活。本研究树立了地热规模化开发的信心，可为雄安新区地热资源安全利用提供支撑。