扬子陆核古元古代变质事件——来自孔兹岩系变质锆石U-Pb同位素年龄的证据

崆岭杂岩除太古宙结晶基底外,还出露一套以含石墨和富铝矿物为特征的孔兹岩系。相对于结晶基底,目前对于该套表壳岩系的同位素年代学研究有限。对该套孔兹岩系中代表性岩石类型榴线英岩开展了变质锆石U-Pb同位素年龄测定。研究结果表明,榴线英岩变质年龄为1964±12Ma。结合前人在相近地层岩石组合中报道的锆石U-Pb年龄数据,推测崆岭杂岩孔兹岩系原岩可能沉积于2.1~2.0Ga。扬子陆核的古元古代变质-岩浆作用可能与全球广泛存在的同时期(2.1~1.8Ga)碰撞造山事件有关,暗示其很可能是Columbia超大陆的重要组成部分。     

The pre-Caledonian Inishkea Division of northwest Co. Mayo,Ireland: Its geochemistry and probable stratigraphic position

The dominantly metasedimentary schists and gneisses of the Inishkea Division of the Erris Complex form a distinct rock group, structurally overlying the Grenvillian Annagh Division orthogneisses and underlying Dalradian metasediments, in the northwest County Mayo metamorphic inlier. A regression line for the Inishkea Division schists, defined by Rb–Sr whole rock analysis, suggests a metamorphic age of about 800 Ma, with a provenance age of about 1000–1300 Ma. The major and trace element chemistry is distinct from both the Annagh Division and Dalradian rocks, although sometimes similar to that of the Erris Group, and it suggests that the Inishkea Division originated as greywackes with associated intrusives. Local variations of the chemistry exist, but no systematic subdivision of the Division has been made. Amphibolite pods within the schists are metamorphosed and deformed tholeiite dykes, which are similar in chemistry to the younger metadolerites seen in the Annagh Division. While the geochemistry suggests that the Inishkea Division rocks are similar to both the Moine Assemblage and Grampian Group rocks of Scotland, the isotopic data suggest that they may have been deposited and then initially metamorphosed during the interval between the Grenville metamorphism of the Moine Assemblage and the onset of Dalradian and Erris Group deposition.     

安徽青阳—九华山复式岩体的成因及成矿潜力——来自锆石Hf同位素和微量元素的证据

青阳—九华山复式岩体是安徽南部地区出露面积最大、最具代表性的复式岩体,该复式岩体的岩浆源区、岩石成因和成矿联系等问题仍需要进一步查明。在前期对青阳—九华山复式岩体的地质、地球化学特征研究基础上,本文进一步开展了锆石微量元素与Hf同位素分析与研究。结果显示,青阳—九华山复式岩体4个阶段从早到晚（花岗闪长岩二长花岗岩正长花岗岩细粒花岗斑岩）,晚期(第三、第四阶段)比早期(第一、第二阶段)岩浆岩的锆石εHf（t）值呈显著增高趋势,岩浆形成温度升高（705.3℃ 715.9℃ 827.1℃ 805.5℃）,氧逸度降低（93.8 149.170.1 69.9）。进一步分析认为,青阳—九华山复式岩体源于同一具有壳幔混源的岩浆源区,随着时间的演化,岩浆房中幔源组分比例逐渐增高,幔源物质的加入,不仅提高了晚期岩浆形成温度,一定程度改变了源区组成。青阳—九华山复式岩体4个阶段花岗岩均经历了榍石、角闪石、金红石、斜长石等矿物的分离结晶,晚期（第三、第四阶段）花岗岩相比早期（第一、第二阶段）花岗岩具有更高的分异程度。青阳—九华山复式岩体中第一、第二阶段花岗岩具有较好的W—多金属矿床成矿潜力。     

早元古陡岭群变质杂岩的岩石地球化学特征

河南省淅川县大陡岭至西峡县田关一带分布的陡岭群变质杂岩,由角闪岩相的变质岩石组成,主要包括片麻岩、钙硅酸粒岩、斜长角闪岩,夹少量的大理岩、石墨片岩和极少量的石英岩。岩石地球化学特征表明：片麻岩的原岩为一套泥砂质的沉积碎屑岩,具有后太古沉积岩的组成特点,形成于活动大陆边缘环境;透辉石变粒岩的原岩为钙砂质的沉积碎屑岩,但可能与片麻岩有着不同的物源区;斜长角闪岩有明显不同的两种产出状态和不同的两类稀土模式,一类呈夹层状与片麻岩互层产出,总稀土含量较低和不强的轻重稀土分离,原岩为非大洋型的拉斑玄武质火山岩;另一类则呈透境状产出,并具有很高的总稀土含量和强的轻重稀土分离,及明显的Ｅｕ负异常,原岩为拉斑玄武质的深成侵入岩。陡岭群变质杂岩有与秦岭群类似的岩石组合、原岩建造和时代等特征,形成于非大洋的活动大陆边缘环境。     

汉南杂岩与金成矿特征

汉南杂岩区位于扬子地台北缘,围岩为元古界绿片岩 勉县—洋县深大断裂系统在成岩、成矿与盆地形成方面占有重要的地位.杂岩体由斜长花岗岩、二长花岗岩、钾长花岗岩、石英闪长岩和辉长辉绿岩组成.金矿化类型主要有石英脉型和蚀变岩型,与接触带、断裂带、蚀变带有关,蚀变后岩石矿物成分变化.使金重新分布,砂金分布与金源、地貌和新构造运动关系密切.     

Retrieval of vertical wind profiles during monsoon from satellite observed winds over the Indian ocean using complex EOF analysis

The aim of this paper is to study the feasibility of deriving vertical wind profiles from current satellite observations. With this aim, we carried out complex empirical orthogonal function (CEOF) analysis of a large number of radiosonde observations of wind profiles over the Indian Ocean during the monsoon months. It has been found that the first two CEOFs explain 67% of the total variance in wind fields. While the first principal component is well correlated with the winds at 850 mb (r = 0:80), the second one is highly correlated with winds at 200 mb (r = 0:89). This analysis formed the basis of a retrieval algorithm which ensures the retrieval of vertical profiles of winds using satellite tracked cloud motion vector winds. Under the assumption that accurate measurements of wind are available at the above mentioned levels, the r.m.s. error of retrieval of each component of wind is estimated to range between 2 ms^-1 and 6 ms^-1 at different levels, which is much less than the natural variance of winds at these levels. For a better visualization of retrieval, we have provided retrieved and true wind profiles side by side for four typical synoptic conditions during the monsoon season.     

P–T evolution of the Precambrian Metamorphic Complex,NW Iran: a study of metapelitic rocks

The Mahneshan Metamorphic Complex (MMC) is one of the Precambrian terrains exposed in the northwest of Iran. The MMC underwent two main phases of deformation (D₁ and D₂) and at least two metamorphic events (M₁ and M₂). Critical metamorphic mineral assemblages in the metapelitic rocks testify to regional metamorphism under amphibolite‐facies conditions. The dominant metamorphic mineral assemblage in metapelitic rocks (M₁) is muscovite, biotite I, Garnet I, staurolite, Andalusite I and sillimanite. Peak metamorphism took place at 600–620°C and ∼7 kbar, corresponding to a depth of ca. 24 km. This was followed by decompression during exhumation of the crustal rocks up to the surface. The decrease of temperature and pressure during exhumation produced retrograde metamorphic assemblages (M₂). Secondary phases such as garnet II biotite II, Andalusite II constrain the temperature and pressure of M₂ retrograde metamorphism to 520–560°C and 2.5–3.5 kbar, respectively. The geothermal gradient obtained for the peak of metamorphism is 33°C km⁻¹, which indicates that peak metamorphism was of Barrovian type and occurred under medium‐pressure conditions. The MMC followed a ‘clockwise’ P–T path during metamorphism, consistent with thermal relaxation following tectonic thickening. The bulk chemistry of the MMC metapelites shows that their protoliths were deposited at an active continental margin. Together with the presence of palaeo‐suture zones and ophiolitic rocks around the high‐grade metamorphic rocks of the MMC, these features suggest that the Iranian Precambrian basement formed by an island‐arc type cratonization. Copyright © 2010 John Wiley & Sons, Ltd.     

Pre-Caledonian basement in Ireland and its cover relationships

Pre-Caledonian basement is exposed in three areas within the Irish orthotectonic Caledonides: 1. In northwest County Mayo the Erris Complex comprises the Annagh Division, which is largely Grenvillian but includes older gneisses, and the Inishkea Division, which is probably equivalent to the older Moines of Scotland. 2. In the northeast Ox Mountains, Rosses Point and Lough Derg inliers there is a granulite fades, dominantly metasedimentary basement which is probably late Grenville in age. 3. Laxfordian and probably older gneisses are seen in the Inishtrahull Platform northeast of Malin Head, County Donegal. In addition, some gneisses within the belt of ‘Connemara migmatites’ in south Connemara may be fragments of allochthonous basement and some high grade metamorphic rocks in the Tyrone Central inlier have been referred to as pre-Caledonian basement, but there is at present no conclusive support for these suggestions. The Ox Mountains succession seen in the Clew Bay region and the southwest and central Ox Mountains is probably not pre-Caledonian basement. Basement in the paratectonic Caledonides is confined to the Cadomian and possibly pre-Cadomian Rosslare Complex (older than 625 Ma) and the nearby late Precambrian (to early Cambrian ?) Cuilenstown Formation in southeast County Wexford. In addition, an unseen block of basement defined by magnetics immediately to the north of the Dingle peninsula of County Kerry is probably of Rosslare Complex affinity. Granulite facies xenoiiths recovered from volcanic rocks of Carboniferous age about 70 km to the west of Dublin, indicate the character of basement there, though its age is not proven. All contacts between basement and Lower Palaeozoic Caledonian cover in the orthotectonic Caledonides are synmetamorphic slide zones and faults and in the paratectonic Caledonides the contacts are either faults, which are often rooted in older mylonites, or are unexposed and presumed to be major structural breaks.     

云南洱源明月—溪灯坪热泉型金矿

明月—溪灯坪金矿金源来自苍山群,受深部岩浆岩期后热液影响后被活化,以络离子形式迁移而形成含金热液,最后在上新统三营组中析出淀积成矿。     

Petrology of alkali basalts of Zlot, Timok Magmatic Complex (Eastern Serbia)

Alkali basalts were discovered in the Timok Magmatic Complex only in a borehole near Zlot. They are composed of plagioclase and clinopyroxene phenocrysts lying in intersertal to pilotaxitic groundmass. The characteristic feature of these rocks is the high content of needle shaped magnetite.

Various disequilibrium features in alkali basalt of Zlot reflect complex convection effects and recharge, most probably in a shallow magma chamber. Major and trace elements data indicate that alkali basalts of Zlot originated from magmas deriving from metasomatized mantle wedge above a subducting and dehydrating plate. However the investigated rocks did not originate from primary magmas, but from a magma which has undergone considerable fractional crystallization.