内蒙古东南部早三叠世花岗岩带岩石地球化学特征及其构造环境

锆石U-Pb定年结果表明位于林西县北西的转山子岩体的形成时代为245.6±0.9Ma,该岩体与内蒙古东南部的龙头山和建设屯岩体共同构成一条大致平行于西拉木伦河蛇绿岩带的早三叠世花岗岩带。岩石学和地球化学分析表明,上述早三叠世岩体属于钙碱性和高钾钙碱性系列,铝饱和指数(ACNK)均小于1.1,属于偏铝质或弱过铝质的I型花岗岩。其中,转山子岩体轻重稀土分馏较弱,含有较低的Sr含量(400×10-6),显示经典岛弧岩石的特征;建设屯岩体具有强烈的轻重稀土分馏以及较高的Sr含量(400×10-6),显示埃达克岩的地球化学特征;龙头山岩体的轻重稀土分馏特征和Sr的含量总体介于前两者之间。锆石Hf同位素分析表明,上述三个岩体都具有正的εHf(t)值。岩石地球化学特征反映它们起源于不同深度的新生下地壳不同程度的部分熔融作用。综合考虑区域地层和岩浆岩资料,本文认为该花岗岩带与区域上同时代的镁铁质火山岩共同形成于西伯利亚和中朝古板块碰撞造山过程中与伸展有关的地球动力学环境,可能与向南俯冲的古亚洲洋板块在早三叠世的断离引起的软流圈上涌有关。     

Distribution of 238U, 232Th and 40K in plutonic rocks of Greece

One hundred and twenty one samples from every major plutonic body (mainly granitic) of Greece have been analyzed by γ-ray spectrometry to determine the specific activities of ²³⁸U, ²³²Th and ⁴⁰K (Bq/kg). The range of the activity concentrations of these radionuclides was 2.3–266.4, 1.8–375.5 and 55.0–1632.0 Bq/kg and their average values were 79.2, 85.3 and 881.4 Bq/kg respectively. Any possible connection between the specific activities of ²³⁸U, ²³²Th and ⁴⁰K and some characteristics of the studied samples (age, rock-type, colour, grain-size, occurrence and chemical composition) is investigated. Samples of particular colour, rock-type, occurrence and chemical composition have been identified for their distinctive levels of natural radioactivity, while age and grain-size do not affect the concentrations of ²³⁸U, ²³²Th and ⁴⁰K. The range of the Th/U ratio was 0.7–12.69. This great variation in the Th/U ratios, especially when it is found among the samples of the same pluton, is also discussed and explained by alteration and tectonic–metamorphic processes.     

大兴安岭北段喀喇其花岗斑岩体地球化学特征、锆石U-Pb年龄及构造背景

本文对大兴安岭北部喀喇其花岗斑岩体进行了岩石学、地球化学及锆石U-Pb年代学的研究,探讨了其形成的构造背景。结果表明:喀喇其花岗斑岩体锆石U-Pb年龄为132 Ma±1 Ma,表明其形成时代应为早白垩世晚期;岩石具有高钾钙碱性系列,过铝质特征;稀土元素属于轻稀土富集型,分布模式为右倾、左陡右平型式,具有较明显的Eu负异常特征。认为该花岗岩为铝质A型花岗岩,属于地壳岩石部分熔融的产物;该期岩浆侵位活动受蒙古—鄂霍茨克构造体系影响,形成于后造山大陆弧或后碰撞弧环境。     

Magmatic control on the contrasting Sn feritility of different granite plutons in the giant Gejiu orefield.SCIEI北大核心CSCD

云南个旧锡矿是全球最大的锡多金属矿床之一,但矿区内同时代花岗岩成锡矿潜力差异显著,其控制因素仍不清楚。本文选取贫矿的龙岔河似斑状花岗岩和成锡矿的老厂-卡房(后文简称老-卡)花岗岩为研究对象,通过全岩地球化学成分和黑云母成分分析,系统研究个旧矿区不同花岗岩成锡矿潜力差异的控制因素。测试结果表明,龙岔河花岗岩和老-卡花岗岩具有相似的、以表壳物质为主的岩浆源区以及较高的初始熔融温度,表明岩浆源区和熔融条件不是控制二者成矿潜力差异的主要原因。黑云母成分显示老-卡花岗岩和龙岔河花岗岩均具有较低的氧逸度,岩浆演化过程中锡为不相容元素,有利于锡在残余熔体中富集,表明氧逸度条件也不是导致成矿潜力差异的关键因素。龙岔河花岗岩发育角闪石、榍石、黑云母,而老-卡花岗岩发育岩浆白云母,指示后者分异程度更高。此外,与龙岔河花岗岩相比,老-卡花岗岩具有富硅,贫钛、铁、镁、钙和稀土元素特征,稀土元素呈现“海鸥式”配分模式,并且具有较低的Nb/Ta、Zr/Hf、K/Rb和较高的Rb/Sr比值,同样指示老-卡花岗岩具有更高的结晶分异程度。并且相比于龙岔河花岗岩为准铝质的特征,老-卡花岗岩的过铝质特征有利于锡分配进入岩浆出溶的流体相中富集成矿。因此,岩浆性质和演化程度是导致个旧地区不同花岗岩成矿潜力差异的主要原因,龙岔河花岗岩形成锡矿化的潜力较小。     

东川拖布卡金矿矿化层位与找金方向

超大型拖布卡金矿的发现,表明东川地区具备找金前景.“黑层”是金的成矿前提,断裂加蚀变是成矿必备条件,基性与中性岩脉在容矿层中的侵位,是找富金的重要标志.金成矿全过程应是多旋回（晋宁、华力西、燕山、喜马拉雅山）成矿作用,且受剪切破碎带控制的黑层型金矿.     

Misconceptions about the Hubble recession law

Almost all astronomers now believe that the Hubble recession law was directly inferred from astronomical observations. It turns out that this common belief is completely false. Those models advocating the idea of an expanding universe are ill-founded on observational grounds. This means that the Hubble recession law is really a working hypothesis. One alternative to the Hubble recession law is the tired-light hypothesis originally proposed by Zwicky (Proc. Nat. Acad. Sci. 15:773, 1929). This hypothesis leads to a universe that is an eternal cosmos continually evolving without beginning or end. Such a universe exists in a dynamical state of virial equilibrium. Observational studies of the redshift-magnitude relation for Type Ia supernovae in distant galaxies might provide the best observational test for a tired-light cosmology. The present study shows that the model Hubble diagram for a tired-light cosmology gives good agreement with the supernovae data for redshifts in the range 0<z<2. This observational test of a static cosmology shows that the real universe is not necessarily undergoing expansion nor acceleration. An erratum to this article can be found at     

The thermal conductivity for granite with various water contents

The thermal conductivities of granite were measured under different conditions of porosity and water content to investigate the effects of the porosity and water content on the thermal conductivity. For the dry samples, the thermal conductivities range from 2.12 W/mK for the rocks with a high porosity to 3.12 W/mK for the ones with a low porosity. Water-sorbed samples have greater thermal conductivities than dry samples of the same granite. The thermal conductivities range from 2.99 W/mK for granites with a high porosity to 3.62 W/mK for ones with a low porosity under saturated condition.     

山阳色河花岗岩地球化学特征和锆石SHRIMP U Pb年代学

山阳色河二长花岗岩出露于泥盆纪地层中,并与泥盆纪地层呈断层接触关系.花岗岩主要由钾长石、斜长石和石英组成,其SiO_2含量介于71%～77%之间、高碱(K_2O+Na_2O＝7.43%～8.50%),低CaO(0.25%～2.81%),为高钾钙碱性花岗岩,A/CNK的平均值为<1.05,属弱过铝质岩石;较强的轻、重稀土元素分馏程度[(La/Yb)_N=4.23],明显的Eu负异常(δEu＝0.511),富集Rb、Th、K、La和Cs等大离子亲石元素,亏损Ba、Nb、Sr、P和Ti元素为特征,属后碰撞花岗岩类.在泥盆纪地层中的花岗岩砾石的岩石地球化学与色河二长花岗岩具有形似性质,高精度的锆石SHRIMPⅡU-Pb定年获得花岗岩与花岗岩砾石形成时代相一致,分别为709±5Ma和700±11Ma.山阳后碰撞花岗岩的发现,标志着新元古代在东秦岭地区表现为造山后伸展拉张阶段,从而为东秦岭造山带从元古代到古生代的构造体制转换提供证据.     

Geochemical, Sr–Nd and zircon U–Pb–Hf isotopic studies of Late Carboniferous magmatism in the West Junggar, Xinjiang: Implications for ridge subduction?

Voluminous granitic intrusions are distributed in the West Junggar, NW China, and they can be classified as the dioritic rocks, charnockite and alkali-feldspar granite groups. The dioritic rocks (SiO₂ = 50.4–63.8 wt.%) are calc-alkaline and Mg enriched (average MgO = 4.54 wt.%, Mg^# = 0.39–0.64), with high Sr/Y ratios (average = 21.2), weak negative Eu (average Eu/Eu = 0.80) and pronounced negative Nb–Ta anomalies. Their Sr–Nd and zircon Hf isotopic compositions ((⁸⁷Sr/⁸⁶Sr)_i = 0.7035–0.7042, ε_Nd(t) = 4.5–7.9, ε_Hf(t) = 14.1–14.5) show a depleted mantle-like signature. These features are compatible with adakites derived from partial melting of subducted oceanic crust that interacted with mantle materials. The charnockites (SiO₂ = 60.0–65.3 wt.%) show transitional geochemical characteristics from calc-alkaline to alkaline, with weak negative Eu (average Eu/Eu = 0.75) but pronounced negative Nb–Ta anomalies. Sr–Nd and zircon Hf isotopic compositions ((⁸⁷Sr/⁸⁶Sr)_i = 0.7037–0.7039, ε_Nd(t) = 5.2–8.0, ε_Hf(t) = 13.9–14.7) also indicate a depleted source, suggesting melts from a hot, juvenile lower crust. Alkali-feldspar granites (SiO₂ = 70.0–78.4 wt.%) are alkali and Fe-enriched, and have distinct negative Eu and Nb–Ta anomalies (average Eu/Eu = 0.26), low Sr/Y ratios (average = 2.11), and depleted Sr–Nd and zircon Hf isotopic compositions ((⁸⁷Sr/⁸⁶Sr)_i = 0.7024–0.7045, ε_Nd(t) = 5.1–8.9, ε_Hf(t) = 13.7–14.2). These characteristics are also comparable with those of rocks derived from juvenile lower crust. Despite of the differences in petrology, geochemistry and possibly different origins, zircon ages indicate that these three groups of rocks were coevally emplaced at ~ 305 Ma.A ridge subduction model can account for the geochemical characteristics of these granitoids and coeval mafic rocks. As the “slab window” opened, upwelling asthenosphere provided enhanced heat flux and triggered voluminous magmatisms: partial melting of the subducting slab formed the dioritic rocks; partial melting of the hot juvenile lower crust produced charnockite and alkali-feldspar granite, and partial melting in the mantle wedge generated mafic rocks in the region. These results suggest that subduction was ongoing in the Late Carboniferous and, thus support that the accretion and collision in the Central Asian Orogenic Belt took place in North Xinjiang after 305 Ma, and possibly in the Permian.     

Fractal analysis of quartz grain boundary sutures in a granite (Malanjkhand,Central India) — Implications to infer regional tectonics

In the present paper the intensity of serration of quartz grain boundary sutures in the Palaeoproterozoic age Malanjkhand granite (Central India) is quantified using the ruler method of fractal analyses. The northern margin of the granite has proximity to the Central Indian Suture (CIS) that forms the southernmost part of Central Indian Tectonic Zone (CITZ) along which amalgamation of the northern and southern Indian shields took place. The fractal dimension (D) of the quartz sutures is calculated in 13 samples collected at varying distance from the CIS. D values are noted to increase in samples towards the CIS. This demonstrates the influence of the tectonic events along the CIS on fabric development in the Malanjkhand granite. Magmatic fabric defined by preferentially oriented feldspar laths and high-T solid-state deformation fabrics are observed in areas distant from the CIS. In contrast, mylonites and low-T fabrics such as bulging quartz grain boundaries occur in proximity to the CIS. It is inferred that the emplacement and high-T fabric development in the Malanjkhand granite was synchronous with regional accretionary processes that occurred in the region during the Palaeoproterozoic. Two different possibilities, one involving a single tectonic event and the other involving multiple tectonic events are discussed to explain the superimposition of low-T over high-T fabric due to which intensity of quartz grain boundary serration increases towards the CIS.