Base-metal deposits of the Cordillera Negra, department of Ancash, Peru

The Cordillera Negra, the westernmost range in the Departamento de Ancash, is just north of the central mineral province of Peru. Within several kilometers of its crest and along a length of 140 kllometers are more than 60 base-metal deposits that total several hundred veins. These deposits were studied in 1947 by the Umted States Geological Survey m cooperation with the Instituto Geológico del Perú. Ores in the deposits contain principally the sulfides of lead and zinc and, in some places, copper, one mine produces antimony ore and another, silver. Basemetal production is wholly dependent on silver content of ore, hence only argentiferous sulfides of lead or copper are sought and sphalerite, which contains little or no silver, is discarded. At the time of our examination, three mines were operated on a comparatively large scale, but one of these subsequently closed, in 1947 the three produced about 37,000 tons of ore, which was concentrated in flotation plants. In the same year fifteen small mines produced probably less than 1,000 tons of ore, which was concentrated by hand cobbing or hand jigging. The deposits in the Cordillera Negra have been worked for many years, so the majority of both large and small active mines now contain small reserves. The reserves of most of the abandoned mines could not be estimated, owing to inaccessibility of their workings. The oldest rocks that can be dated in the Cordillera are Cretaceous in age An estimated 2,200-meter-thick sequence of sedimentary rocks of Early Cretaceous age consists predominantly of nonmarine sandstone and shale but includes several coal beds, a thin unit of limestone, and, toward the top of the sequence, a unit of tuff. These rocks are overlain by Albian to Turonian limestone, estimated to be from 200 to 400 meters thick. This sedimentary sequence is overlain by a sequence of layered volcanic rocks, possibly in part of Late Cretaceous age but mostly of Tertiary age The volcanic rocks are estimated to be at least 1,000 meters thick, lava and agglomerate are the most common rocks, but some tuff and a few beds of nonvolcanic sediments are included in the sequence. Most of the -lava and the agglomerate is porphyritic andesite and most of the tuff is rhyolite. The volcanic sequence can be divided into two groups a lower group includes layers that are moderately closely folded, an upper group includes those that are only slightly folded. The sedimentary and volcanic rocks are intruded by granodwntic and granitic batholiths and stocks, by porphyritic andesite and rhyolite stocks and plugs, and by sills and dikes ranging from pegmatite to andesite in composition. Some sedimentary rock has been converted to andalusite schist near contacts with the batholiths or the larger gramtic stocks. The layered rocks have been deformed during two periods of major orogeny, the first of possible Late Cretaceous or very early Tertiary age, and the second of possible early Tertiary age. Each is marked by a conspicuous unconformity. The lower unconformity is between the sedimentary sequence and the folded lower volcanic group, and the upper is between the folded lower volcanic group and the slightly folded upper volcanic group. Plutonic intrusion of granodiorite and granite and shallow-seated intrusion of porphyry seems to have occurred in the Tertiary Strata of the sedimentary sequence are closely folded and those of the lower volcanic group are moderately closely folded, and strata of both are broken by thrust and reverse faults. Axial planes of folds dip steeply and strike generally N 30° W, parallel to the structural trend of the Andean Cordillera in this part of Peru. Open folds and warps characterize deformation in the upper volcanic group, and are accompanied by steeply dipping normal and reverse faults of small displacement. Only limited regional metamorphism of the older rocks resulted during orogenesis, slaty cleavage is found in some shale. Most deposits are minerahzed fractures containig pyrite, galena, and sphalerite in a gangue of quartz and carbonate, other minerals that may be present are arsenopyrite, chalcopyrite, enargite, or tetrahedrite. Other deposits are quartzpyrite veins, and in some the sulfides commonly are marmatite, pyrrhotite, and pyrite. One vein contains stibnite and pyrite in quartz. Either primary or secondary silver minerals occur in all deposits, in some in sufficient quantities to repay fairly high mining costs, gold also is present in many deposits but generally in insignificant amounts. Nearly all minerals were deposited as fissure-fillings, but some replaced wall-rock on a small scale in several veins. Alteration in most deposits was slight and altered zones are confined to adjacent wall-rock. Several deposits, however, occur in widespread altered zones. Textures and the prevalence of low-temperature minerals suggest that the deposits were formed at shallow depths, and that the vertical range of ore deposition was small. Minining discloses the maximum range was almost 600 meters At several mines zoning is well developed in both vertical and horizontal dimensions, in distances as small as 200 meters. The type of minerals, degree of crystalhnity, and vein structures indicate that the veins formed at shallow depths under conditions of moderate to low temperature and pressure, and thus can be classed as ranging from mesothermal to epithermal. Although 600 meters is about the maximum vertical range of strongly mineralized deposits, most veins do not reach this depth Veins range in length from several meters to 2.5 kilometers, and range in width from several centimeters to many meters. Lenticular ore shoots of irregular sizes and shapes occupy only small parts of most veins, this precludes any great increase in the rate at which ore is mined

Excessive heart rate increase during mild mental stress in preparation for exercise predicts sudden death in the general population

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Purification from human plasma of a tetrapeptide that potentiates insulin-like growth factor-I activity in chick embryo cartilage

AbstractHuman plasma has been shown to contain a low molecular weight factor that potentiates human IGF-I stimulation of glycosaminoglycan synthesis in chick embryo cartilage. The peptide was purified and characterized by Edman degradation and electrospray mass spectrometry. The primary structure determined was: Trp-Gly-His-Glu. A homologous synthetic peptide similarly promoted matrix biosynthesis in cartilage exposed to IGF-1

Scintillator counters with WLS fiber/MPPC readout for the side muon range detector (SMRD)of the T2K experiment

The T2K neutrino experiment at J-PARC uses a set of near detectors to measure the properties of an unoscillated neutrino beam and neutrino interaction cross-sections. One of the sub-detectors of the near-detector complex, the side muon range detector (SMRD), is described in the paper. The detector is designed to help measure the neutrino energy spectrum, to identify background and to calibrate the other detectors. The active elements of the SMRD consist of 0.7 cm thick extruded scintillator slabs inserted into air gaps of the UA1 magnet yokes. The readout of each scintillator slab is provided through a single WLS fiber embedded into a serpentine shaped groove. Two Hamamatsu multi-pixel avalanche photodiodes (MPPC's) are coupled to both ends of the WLS fiber. This design allows us to achieve a high MIP detection efficiency of greater than 99%. A light yield of 25-50 p.e./MIP, a time resolution of about 1 ns and a spatial resolution along the slab better than 10 cm were obtained for the SMRD counters.Comment: 7 pages, 4 figures; talk at TIPP09, March 12-17, Tsukuba, Japan; to be published in the conference proceeding

The SMRD subdetector at the T2K near detector station

The T2K long-baseline neutrino oscillation experiment is running in Japan. The primary goals of the T2K are measurement of the mixing angle 13, and precise measurements of the mixing angle 23 and of the mass difference m2 23. The installation of the near detector complex was completed and first data were already registered. This article presents operation of the Side Muon Range Detector, a component of the Off-Axis near detector. Detector concept and implementation are presented, followed by a description of cosmic muon track reconstruction algorithm and finally current status

Weaning practices in phenylketonuria vary between health professionals in Europe

Background: In phenylketonuria (PKU), weaning is considered more challenging when compared to feeding healthy infants. The primary aim of weaning is to gradually replace natural protein from breast milk or standard infant formula with solids containing equivalent phenylalanine (Phe). In addition, a Phe-free second stage L-amino acid supplement is usually recommended from around 6 months to replace Phe-free infant formula. Our aim was to assess different weaning approaches used by health professionals across Europe. Methods: A cross sectional questionnaire (survey monkey (R)) composed of 31 multiple and single choice questions was sent to European colleagues caring for inherited metabolic disorders (IMD). Centres were grouped into geographical regions for analysis. Results: Weaning started at 17-26 weeks in 85% (n=81/95) of centres, > 26 weeks in 12% (n=11/95) and 26 weeks. First solids were mainly low Phe vegetables (59%, n=56/95) and fruit (34%, n=32/95). A Phe exchange system to allocate dietary Phe was used by 52% (n=49/95) of centres predominantly from Northern and Southern Europe and 48% (n=46/95) calculated most Phe containing food sources (all centres in Eastern Europe and the majority from Germany and Austria). Some centres used a combination of both methods. A second stage Phe-free L-amino acid supplement containing a higher protein equivalent was introduced by 41% (n=39/95) of centres at infant age 26-36 weeks (mainly from Germany, Austria, Northern and Eastern Europe) and 37% (n=35/95) at infant age > 1y mainly from Southern Europe. 53% (n=50/95) of centres recommended a second stage Phe-free L-amino acid supplement in a spoonable or semi-solid form. Conclusions: Weaning strategies vary throughout European PKU centres. There is evidence to suggest that different infant weaning strategies may influence longer term adherence to the PKU diet or acceptance of Phe-free L-amino acid supplements; rendering prospective long-term studies important. It is essential to identify an effective weaning strategy that reduces caregiver burden but is associated with acceptable dietary adherence and optimal infant feeding development.Peer reviewe

Early feeding practices in infants with phenylketonuria across Europe

Background: In infants with phenylketonuria (PKU), dietary management is based on lowering and titrating phenylalanine (Phe) intake from breast milk or standard infant formula in combination with a Phe-free infant formula in order to maintain blood Phe levels within target range. Professionals use different methods to feed infants with PKU and our survey aimed to document practices across Europe. Methods: We sent a cross sectional, survey monkey (R) questionnaire to European health professionals working in IMD. It contained 31 open and multiple-choice questions. The results were analysed according to different geographical regions. Results: Ninety-five centres from 21 countries responded. Over 60% of centres commenced diet in infants by age 10 days, with 58% of centres implementing newborn screening by day 3 post birth. At diagnosis, infant hospital admission occurred in 61% of metabolic centres, mainly in Eastern, Western and Southern Europe. Breastfeeding fell sharply following diagnosis with only 30% of women still breast feeding at 6 months. 53% of centres gave pre-measured Phe-free infant formula before each breast feed and 23% alternated breast feeds with Phe-free infant formula. With standard infant formula feeds, measured amounts were followed by Phe-free infant formula to satiety in 37% of centres (n = 35/95), whereas 44% (n = 42/95) advised mixing both formulas together. Weaning commenced between 17 and 26 weeks in 85% centres, >= 26 weeks in 12% and <17 weeks in 3%. Discussion: This is the largest European survey completed on PKU infant feeding practices. It is evident that practices varied widely across Europe, and the practicalities of infant feeding in PKU received little focus in the PKU European Guidelines (2017). There are few reports comparing different feeding techniques with blood Phe control, Phe fluctuations and growth. Controlled prospective studies are necessary to assess how different infant feeding practices may influence longer term feeding development.Peer reviewe