http://www.sciencedirect.com/science/article/pii/S1674987113000029

The Preandean geological configuration of the eastern North Patagonian Massif is established through the use of geological and geophysical analysis.The positive gravity anomalies located near the Atlantic coast are due to 535 and 540 Ma old rocks belonging to the Pampean Orogeny （Precambrian-middle Cambrian）,which are widely recognized in central and northern Argentina.The Famatinian Cycle （Ordovician-Devonian） is represented by a Silurian-Devonian marine basin equivalent to those of eastern-central Argentina and South Africa,and which was deformed at the end of the Devonian byan～E-W to WNW-ESE compressional event,part of the Famatinian Orogeny.Containing strong gravity gradients,the NW-SE belt is coincident with fault zones which were originated during the Gondwanide Orogeny.This event also produced NW-SE overthrusting of the Silurian-Devonian sequences and strike-slip faults that displaced blocks in the same direction.This deformation event belongs to the Gondwanide Orogeny that includes movements related to a counterclockwise rotation of blocks in northern Patagonia.The strong negative anomalies located in the western part of the area stem from the presence of rocks of the Jurassic Ca（n）adón Asfalto basin interbedded in the Marifil Complex.These volcaniclastic sequences show mild deformation of accommodation zones in a pre-Jurassic paleorelief.     

The Puesto Piris Formation: Evidence of basin-development in the North Patagonian Massif during crustal extension associated with Gondwana breakup

The Marifil Volcanic Complex, exposed in the eastern North Patagonian Massif, Argentina, includes up to 550 m of red conglomerates, sandstones, black siltstones, limestones, and reworked tuff of the Puesto Piris Formation. The basal part of this unit, which was deposited in high-gradient topographic relief, is composed of conglomerates and sandstones with thin layers of reworked tuffs. The lithofacies associations of the basal part indicate that the depositional mechanisms were mantled and gravitational flows.The middle part of the unit consists of fine sandstones, limestones, and black siltstones that were deposited in low-energy fluvial and lacustrine environments. The outcrops are located along the NEe SW direction and the major thickest units represented by limestones and siltstones, occur near the southeastern border of this NEeS W depocenter. Since the rhyolitic and trachytic lava flows and tuffs of the Marifil Volcanic Complex are interbedded with the sedimentary sequences of the Puesto Piris Formation,both units are coeval. Zircon Ue Pb age was obtained for a trachytic lava flow(193.4 ±3.1 Ma) suggesting that sedimentation and volcanism are Sinemurian. This extensional episode was recorded in the eastern,western, and southwestern sectors of the North Patagonian Massif, and is possibly associated with the Gondwana supercontinent breakup.     

ALB上焦耳热场的形态分布特征及环境意义探讨

利用地磁场MAGSAT（1980）模型计算了软流圈-岩石圈边界（ALB）上的焦耳热场，分析了它的形态分布特征，并探讨了其环境意义。发现ALB上焦耳热高值中心的分布与全球地热带和火山的分布有较好的一致性，焦耳热的水平尺度与地热涡的水平尺度、我国大陆上多雨带的间距及降水量和气温的高相关带的间距相当。低纬地带ALB上焦耳热中心的分布与全球平均年最大降水量中心的分布特征有很好的对应。另外，ALB上全球最大焦耳热中心位于我国青藏高原东南部的热点上。最后，讨论了地磁与气候的可能联系。     

A cervelleite-like mineral and other Ag-Cu-Te-S minerals [Ag2CuTeS and (Ag,Cu)2TeS] in gold-bearing veins in metamorphic rocks of the Cycladic Blueschist Unit, Kallianou, Evia Island, Greece

A cervelleite-like mineral, two unnamed silver sulfotellurides in the system Ag-Cu-Te-S [Ag₂CuTeS, (Ag,Cu)₂TeS], Te-rich polybasite and cadmian tetrahedrite occur in gold-bearing quartz veins in metapelites and faults within brecciated marbles of the Cycladic Blueschist Unit in the Kallianou area (southern Evia Island, Greece). The quartz veins and faults are discordant to syn-metamorphic structures and formed during ductile to brittle deformation in the final stages of exhumation of the Styra Nappe extrusion wedge (~21?Ma). Te-rich polybasite (up to 7.4 wt. % Te), cadmian tetrahedrite (up to 12.4 wt. % Cd), together with electrum (23?C54 wt. % Ag) and the sulfotellurides, are the main silver carriers in the mineralization. The two unnamed sulfotellurides, Ag₂CuTeS and (Ag,Cu)₂TeS are believed to be new quaternary minerals in the system Ag-Cu-Te-S. These minerals and the cervelleite-like phase could have exsolved from galena during cooling (below 200°C). Initial temperatures for the formation of the sulfotellurides, in the form of hessite-intermediate solid solution, at Kallianou may be up to 300°C under logfS₂ values between?~ ?11.5 to ?8.3, and logfTe₂ from?~ ?14.8 to ?7.8. The values of logfTe₂ and logfS₂ during re-equilibration (at ~200°C) were constrained to ?19.5 to ?15.2 and to ?15.8 to ?11.5 respectively.     

New ages from the Mauritanides Belt: recognition of Archean IOCG mineralization at Guelb Moghrein,Mauritania

The Guelb Moghrein Fe oxide–Cu–Au–Co (IOCG) deposit is located in the northern part of the Mauritanides chain at the western edge of the West African Craton. It is commonly held that the orogenic belt has experienced a polyphase tectonothermal evolution, including two Panafrican and one Variscan event. Dating of two distinct morphological types of hydrothermal monazite and xenotime from Guelb Moghrein yielded in situ U–Pb ages of 2492 ± 9 and 1742 ± 12 Myr respectively. Such ages have not been reported previously from the region which is conspicuous by the widespread occurrence of banded iron formations, more akin to Proterozoic or Archean than to Paleozoic settings. The supracrustal rocks are thought, therefore, to represent a greenstone terrane that was mineralized by hydrothermal fluids during the late Archean and reactivated by middle Proterozoic fluid flow. Final emplacement at the current position on the West African Craton was at ～300 Ma during Gondwana–Laurentia collision.     

Nonseparable stationary anisotropic space–time covariance functions

Obtaining new and flexible classes of nonseparable spatio-temporal covariances and variograms has resulted a key point of research in the last years. The goal of this paper is to introduce and develop new spatio-temporal covariance models taking into account the problem of spatial anisotropy. Recent literature has focused on the problem of full symmetry and the problem of anisotropy has been overcome. Here we propose a generalization of Gneiting’s (J Am Stat Assoc 97:590–600, 2002a) approach and obtain new classes of stationary nonseparable spatio-temporal covariance functions which are spatially anisotropic. The resulting structures are proved to have certain interesting mathematical properties, together with a considerable applicability.Work partially funded by grant MTM2004-06231 from the Spanish Ministry of Science and Education.     

Genetic evolution of Permo-Triassic volcaniclastic sequences at Uspallata, Mendoza Precordillera, Argentina

Permo-Triassic volcanic rocks of the Choiyoi Group crop out at Quebrada de Santa Elena and del Telégrafo, Mendoza Precordillera, Argentina. In this area, six volcanic events were generated through three volcanic stages that include collapse of voluminous Plinian columns associated to caldera pressurization and depressurization, emplacement of sub-volcanic bodies and dikes connected to depressurization of the magmatic chamber and establishment of resurgent domes and lava associated to caldera collapse events.

Petrologic and geochemical data indicate increasing acidification toward younger events varying from dacitic to rhyodacitic and rhyolitic rocks. The lithofacial organization allows correlating with the Lower to Upper Permian Horcajo Formation described in the Valle del Río de los Patos, San Juan province. Geochemical data suggests subduction-related arc magmatism in an extensional condition during Lower to Upper Permian.     

Enhanced Cloud Disruption by Magnetic Field Interaction

We present results from the first three-dimensional numerical simulations of moderately supersonic cloud motion through a tenuous, magnetized medium. We show that the interaction of the cloud with a magnetic field perpendicular to its motion has a great dynamical impact on the development of instabilities at the cloud surface. Even for initially spherical clouds, magnetic field lines become trapped in surface deformations and undergo stretching. The consequent field amplification that occurs there and, in particular, its variation across the cloud face then dramatically enhance the growth rate of Rayleigh-Taylor unstable modes, hastening the cloud disruption.