Reconstruction of the mid-Devonian HP-HT metamorphic event in the Bohemian Massif (European Variscan belt)

Mid-Devonian high-pressure (HP) and high-temperature (HT) metamorphism represents an enigmatic early phase in the evolution of the Variscan Orogeny. Within the Bohemian Massif this metamorphism is recorded mostly in allochthonous complexes with uncertain relationship to the major tectonic units. In this regard, the Mariánské Lázně Complex (MLC) is unique in its position at the base of its original upper plate (Teplá-Barrandian Zone). The MLC is composed of diverse, but predominantly mafic, magmatic-metamorphic rocks with late Ediacaran to mid-Devonian protolith ages. Mid-Devonian HP eclogite-facies metamorphism was swiftly followed by a HT granulite-facies overprint contemporaneous with the emplacement of magmatic rocks with apparent supra-subduction affinity. New Hf in zircon isotopic measurements combined with a review of whole-rock isotopic and geochemical data reveals that the magmatic protoliths of the MLC, as well as in the upper plate Teplá-Barrandian Zone, developed above a relatively unaltered Neoproterozoic lithospheric mantle. They remained coupled with this lithospheric mantle throughout a geological timeframe that encompasses separate Ediacaran and Cambrian age arc magmatism, protracted early Paleozoic rifting, and the earliest phases of the Variscan Orogeny. These results are presented in the context of reconstructing the original architecture of the Variscan terranes up to and including the mid-Devonian HP-HT event.     

In situ Lu–Hf phosphate geochronology: Progress towards a new tool for space exploration

Geochronology is fundamental to understanding planetary evolution. However, as space exploration continues to expand, traditional dating methods, involving complex laboratory processes, are generally not realistic for unmanned space applications. Campaign-style planetary exploration missions require dating methods that can (1) rapidly resolve age information on small samples, (2) be applied to minerals common in mafic rocks, and (3) be based on technologies that could be installed on future rover systems. We demonstrate the application of rapid in situ microanalytical Lu–Hf phosphate geochronology using samples of pallasite meteorites, which are representative examples of the deep interiors of differentiated planetoids that are generally difficult to date. Individual pallasites were dated by laser ablation tandem mass-spectrometry (LA-ICP-MS/MS), demonstrating a rapid novel method for exploring planetary evolution. Derived formation ages for individual pallasites agree with traditional methods and have <2% uncertainty, opening an avenue of opportunity for remote micro-analytical space exploration.     

郯庐断裂带的延伸与切割深度

摘要：采用地质 地球化学 地球物理相结合的方法,系统研究了中生代以来郯庐断裂带的延伸长度与切割深度。２５０～２０８Ｍａ期间,郯庐断裂带开始形成,延展长度不超过１５００ｋｍ,切割深度在１５～２０ｋｍ,是以左行走滑活动为主的基底断裂。１３５～５２Ｍａ时期,该断裂带大幅度地扩展了长度（达３５００ｋｍ）,切割深度在３０～４０ｋｍ之间,为略具右行平移活动的正断层,属地壳断裂。２３３Ｍａ以来,断裂带以向下深切为主,深度从５０ｋｍ左右逐渐加深到８０～１００ｋｍ,终于形成岩石圈断裂     

Geochemistry and geochronology of mafic rocks from the Spanish Central System:Constraints on the mantle evolution beneath central Spain

The Spanish Central System(SCS) contains several suites of Palaeozoic mafic igneous intrusions with contrasting geochemical affinity:Ordovician tholeiitic metabasites,Variscan calc-alkaline gabbros(Gb1) and microdiorites(Gb2),shoshonitic monzogabbros(Gb3) and alkaline diabases and lamprophyres(Gb4).Not all of these rocks are accurately dated,and several aspects of their genesis are still poorly understood.We present new whole-rock geochemical data(major and trace elements,and Sr-Nd isotopes),U-Pb and Lu-Hf isotopic ratios on magmatic zircons and 40 Ar/~(39)Ar amphibole geochronology results in order to establish a precise chronology for the successive events of magmatism in the SCS,and discuss the nature of their mantle sources.Accurate ages have been determined for the Variscan gabbros(305-294 Ma),the microdiorites(299 Ma) and the accompanying felsic porphyries(292 Ma),the shoshonitic monzogabbros(285 Ma),and the alkaline diabases(274 Ma) and monzosyenites(271-264 Ma).According to this information,the Variscan mafic magmatism would be mainly concentrated in the range of 305-294 Ma,with a final manifestation represented by the minor shoshonitic dykes.The alkaline magmatism proved to be slightly older than previously thought and yielded at least two distinct pulses:diabases and lamprophyres-monzosyenites.Zircon Hf isotopes evidence the involvement of depleted and slightly enriched mantle sources.The bulk of the eHf values are in the broad range of-8 to+11,indicative of melting both depleted and enriched mantle regions.The high within-sample Hf isotope variation(up to-11 epsilon units) shown by samples from the Variscan series(gabbros,microdiorites and monzogabbros) could be explained mainly by hybridisation of magmas derived from heterogeneous lithospheric mantle sources.Pressure estimates indicate that the Variscan mafic magmas were extracted from the lithosphere.The Nd-Hf isotopic composition of these suites of rocks suggests the recycling of pelitic sediments during the Cadomian orogeny.Deeper(asthenospheric) mantle levels were involved in the generation of the alkaline suite,whose anomalous negative eHf values(moderately decoupled with respect to radiogenic Nd) could be associated with subducted oceanic components raised by mantle upwelling associated with lithosphere thinning and extension during the Permian.     

郯庐断裂带火山活动与深部地质过程的新认识

在郯庐断裂带中生代以来的三期演化中,都伴生了火山活动。早白垩世走滑期的火山活动起源于地幔底侵、壳幔相互作用下的壳幔过渡带,也指示此时的断裂带切入到壳幔边界。断裂带内新生代玄武岩喷发起始于强烈伸展的后期（古新世）,在随后的断裂挤压期达到高温,该玄武岩喷发不但反映了断裂带已深切至上地幔,出现了地幔剪切带,也显示地幔交代,混杂地幔区等重要的深部过程信息。     

郯庐断裂皖中段的韧性活动特征

揭示了皖中浮槎山地区郯庐断裂的韧性活动以产生大规模的韧性剪切带为特征,构造岩为各类糜棱岩,并造成浮槎山的变质变形地质休呈由剪切带围限的透镜状夹块格局,为带逆冲性质的左行平移剪切,形成时代为Ｊ１－２     

江西庐山地区早元古代星子群变质作用和岩石地球化学特征

早元古代星子群遭受吕梁期以低角闪岩相为主的区域动力热流变质作用，变质温度约为５３０－６００℃，压力约为４００－５７０ＭＰａ。根据岩石组合及岩石地球化学特征．推测该群形成于大陆边缘环境。     

U–Pb and Lu–Hf isotope systematics of detrital zircons from the Songpan–Ganzi Triassic flysch,NE Tibetan Plateau: implications for provenance and crustal growth

We conducted in situ U–Pb and Lu–Hf isotope analyses of 401 detrital zircons collected from the Songpan–Ganzi Triassic turbidite complex in an attempt to understand the provenance variations of the siliciclastic rocks and the crustal growth history of central China. These detrital zircons exhibit a wide age spectrum with three major peaks at 1.7–2.0 Ga, 750–1050 Ma, and 210–500 Ma. They are dominated by negative ?_Hf(t) values with a large range. Synthesis of the zircon U–Pb and Lu–Hf isotopic data indicate that the Triassic Songpan–Ganzi turbiditic succession could have been derived dominantly from the Tibetan terrains + the Kunlun and Qinling orogens. Our samples are characterized by a common, prominent group of Hf crust formation model ages at 0.8–4.1 Ga with a peak at 2.7–3.4 Ga. This fact indicates that (1) Phanerozoic magmatism in central China could have been predominantly products of crustal reworking with insignificant formation of juvenile crust and (2) the Neoarchaean was an important period of continental growth in central China. In addition, our data set also reveal that three widespread tectonothermal events could have occurred in the region during the late Mesoproterzoic, Palaeozoic, and early Mesozoic, respectively.     

东海原甲藻吸收光谱特性分析

以东海原甲藻为研究对象,通过室内和室外的一系列培养实验.通过对不同生长时期其光吸收特性的变化和不同光强对其光吸收特性的影响进行研究,分析东海原甲藻先吸收特性研究及其爆发的可能机制.结果表明在培养的不同时期东海原甲藻光吸收特性差异明显,在不同光强条件下,当遮光率为77.7%时,最适于东海原甲藻生长.     

江西庐山风景区旅游气候学透视

天气与气候是影响旅游业发展的关键因素。从旅游气候学角度透视气候对传统避暑胜地庐山旅游业发展的影响,发现当地气候对旅游业的发展具有明显的促进作用,表现在庐山气候的美学属性为当地提供了大量气候旅游资源,另一方面气候的旅游适宜性为吸引海内外游客奠定了坚实基础。但庐山的气候对旅游业发展也有一定制约作用,如气候诱发的明显旅游季节性和某些极端天气事件。为了促进庐山旅游业的可持续发展,未来应大力开发反季节旅游产品,改变传统旅游目的地形象,加大季节性差异定价力度,优化旅游产品结构,提高灾害性天气防御能力。