Arequipa, Peru
Arequipa, Peru

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Roperch P.,IRD | Roperch P.,University of Rennes 1 | Carlotto V.,INGEMMET | Ruffet G.,French National Center for Scientific Research | And 2 more authors.
Tectonics | Year: 2011

We report new paleomagnetic results from 55 out of 76 sites sampled at different localities along a transect from Nazca to Cuzco where the general structures of the Peruvian Andes are strongly offset across the Abancay deflection. Nine new 39Ar/40Ar ages better constrain the timing of volcanism along the western edge of the Western Cordillera at the latitude of Nazca. A mean paleomagnetic result from 22 sites in the lower Miocene volcanics does not show significant rotation (R = -2.3° ± 7.7°) of the western margin of the Central Andean Plateau since the early Miocene. Within the Western Cordillera we sampled three structural blocks bounded to the north by the Abancay fault system. In the westernmost block, a large counterclockwise rotation (R = -65.0° ± 11.1°) is found in Mesozoic limestones and Paleocene-Eocene red beds. Magnitude of rotation decreases toward the east from (R = -35.6° ± 12.8°) in the central block to (R = -4.5° ± 8.4°) south of the town of Cuzco. The anisotropy of magnetic susceptibility (AMS) recorded by the red beds sediments is the consequence of compaction and tectonic strain during the early stages of deformation. We show that the magnetic lineations were also rotated counterclockwise as the remanent magnetizations. The present study confirms results from the Peruvian fore arc, showing that rotations are not older than circa 40 Ma and likely not younger than circa 20 Ma. The spatial variation in the amount of counterclockwise rotation suggests a large component of shear along the Abancay deflection concomitant with a broad late Eocene-Oligocene oroclinal deformation in southern Peru. Copyright 2011 by the American Geophysical Union.

Byrdina S.,University of Savoy | Ramos D.,INGEMMET | Vandemeulebrouck J.,University of Savoy | Masias P.,INGEMMET | And 7 more authors.
Earth and Planetary Science Letters | Year: 2013

Present work studies the influence of the regional topography on the hydrothermal fluid flow pattern in the subsurface of a volcanic complex. We discuss how the advective transfer of heat from a magmatic source is controlled by the regional topography for different values of the averaged permeability. For this purpose, we use a 2-D numerical model of coupled mass and heat transport and new data sets acquired at Ticsani and Ubinas, two andesitic volcanoes in Southern Peru which have typical topography, justifying this approach. A remarkable feature of these hydrothermal systems is their remote position not centered on the top of the edifice. It is evidenced by numerous hot springs located in more than 10. km distance from the top of each edifice. Upwelling of thermal water is also inferred from a positive self-potential anomaly at the summit of the both volcanoes, and by ground temperatures up to 37 °C observed at Ticsani. Our model results suggest that the regional topographic gradient is able to significantly divert the thermal water flow and can lead to an asymmetric emplacement of the hydrothermal system even considering a homogeneous permeability of the edifice. Inside the thermal flow, the hydraulic conductivity increases with the decrease of temperature-related viscosity, focusing the flow towards the surface and creating a hydrothermal zone at a large lateral distance from the heat source. The location and temperature of the hot springs together with the water table position given by self-potential data can be used to constrain the average permeability of the edifice, a key parameter influencing fluid flow and associated advective heat transfer in the direction opposite to the regional topographic gradient. Our study allows to explain the emplacement of the hydrothermal systems at volcanoes with asymmetric edifices or even the absence of a shallow hydrothermal system. These results can be generalized to the study of non-volcanic hydrothermal systems. © 2013 Elsevier B.V.

Lacroix P.,French National Center for Scientific Research | Berthier E.,LEGOS | Maquerhua E.T.,INGEMMET
Remote Sensing of Environment | Year: 2015

Major earthquakes in mountainous areas often trigger rapid landslides. Some observations also suggest that earthquakes can damage landslide prone areas or cause slow-moving landslides to accelerate, with a risk of evolution to rapid landslides in the following months after the earthquake. Here, we use optical images from the Pléiades satellites to detect slow-moving landslides and quantify the effect of earthquakes on the landslide motion. We process multi-temporal Pléiades images acquired in March, April, and July 2013 over an area of 210km2 in the Colca valley (South Peru), to obtain two Digital Elevation Models (DEM) and three displacement fields of the area. The processed DEMs have an uncertainty of 0.6m (1σ), an order of magnitude better than two global and freely available DEMs (GDEM-v2 and SRTM), whereas the displacement fields have an uncertainty of between 0.11 and 0.18m (1σ) in both horizontal directions. Using these data, we detect 9 slow-moving landslides and compare their velocities during the March-April and April-July periods. We find that landslide velocities are highest during the wet season, which suggests a strong groundwater control, and we also highlight a landslide acceleration caused by a regional Mw 6.0 earthquake. The major parameters controlling the acceleration of the slow-moving landslides are the rock type and the distance to the source, suggesting that friction at the basal interface in the weeks after the earthquake is dependent on the shaking intensity. © 2015 Elsevier Inc..

Bahlburg H.,University of Munster | Vervoort J.D.,Washington State University | Andrew DuFrane S.,Washington State University | Andrew DuFrane S.,University of Alberta | And 4 more authors.
Journal of South American Earth Sciences | Year: 2011

The Ordovician Ollantaytambo Formation represents one of only two known occurrences of Lower Paleozoic volcanic rocks in southern Peru and northern Bolivia. Its lower part consists of mafic lapilli tuffs, shales and mature sandstones form the upper part. We present LA-ICP-MS U-Pb ages and Hf isotope data of detrital zircons from one of the upper member sandstones in order to determine both the duration of volcanism and the provenance of the mature detritus, and to use the data to further define the paleogeography of the Ordovician basin in the northern Central Andes. The detrital zircon ages of the Ollantaytambo Formation range from 2013 Ma to 445 Ma. They are grouped mainly between 1400 and 1100 Ma (35%), 1100 and 900 Ma (14%), 770 and 650 Ma (14%), and from 500 Ma to 440 Ma (30%). Within these groups the main peaks are at 1249 Ma, 1052 Ma, 741 Ma and 459 Ma. The older groups correspond to major orogenic cycles recorded on the southwestern Amazonia craton, the Rondonia-San Ignacio, Sunsás, and Brasiliano orogenies. The younger one reflects the activity of the Early Paleozoic Famatinian magmatic arc known mainly from the southern Central Andes, but also recognized on the Arequipa Massif and in northern Peru. The provenance of the grains with ages between 770 Ma and 650 Ma is enigmatic as there are no known sources in southwestern Amazonia or the Central Andes.The e{open}Hf(t) values of selected Ollantaytambo Formation zircons are between -22 and +3 and considered to be moderately juvenile to evolved. Truely juvenile zircons with a composition similar to the depleted mantle were not identified. Together with additional literature data from Ordovician formations in southern Peru, the Hf-isotope data indicate production of juvenile crust mainly in the Mesoproterozoic, and increasing recycling of this crust during the Neoproterozoic and Early Paleozoic orogenic events. © 2011 Elsevier Ltd.

Reimann C.R.,University of Munster | Bahlburg H.,University of Munster | Kooijman E.,University of Munster | Berndt J.,University of Munster | And 3 more authors.
Gondwana Research | Year: 2010

We present results of a combined study of in situ U-Pb and Lu-Hf analyses on detrital zircons of Ordovician to Devonian sandstone successions of the Eastern Cordillera of Peru and Bolivia, as well as of the Altiplano and Coastal Cordillera of Peru (14°-17°S). We use our data to constrain the provenance and tectonic evolution of this part of the Gondwana margin in the early Paleozoic. The zircon-age composition is very variable in the different locations. Sandstones of the Eastern Cordillera have a dominant input of Brazilian-age zircons (0.7-0.5Ga) with two prominent peaks at around 0.52- 0.58Ga and 0.61-0.67Ga. A prevailing eastern source (Brazilian Shield, Amazonian Craton) is inferred. In contrast, sandstones from the Coastal Cordillera and Altiplano have major inputs of Famatinian (0.5-0.4Ga), Grenvillian (1.2-0.9Ga) and occasionally zircons of 1.85-1.75Ga crystallisation ages. Here, a dominant provenance from the Arequipa Massif is likely. Zircons preserving a juvenile component with εHf(t) values range from about +12 to +6 are limited to crystallisation ages between 1.45 and 1.0 Ga. All younger grains have lower εHf(t) values consistent with recycling of old crust without juvenile additions during the Neoproterozoic. Brazilian-age zircons of an Amazonian craton provenance and Famatinian-age zircons of an Arequipa Massif provenance have similar Hf model ages suggesting their derivation from the same evolved crust. © 2010 International Association for Gondwana Research.

Lacroix P.,French National Center for Scientific Research | Zavala B.,INGEMMET | Berthier E.,French National Center for Scientific Research | Audin L.,French National Center for Scientific Research
Remote Sensing | Year: 2013

Earthquake is one of the dominant triggering factors of landslides. Given the wide areas covered by mega earthquake-triggered landslides, their inventory requires development of automatic or semi-automatic methods applied to satellite imagery. A detection method is here proposed for this purpose, to fit with simple datasets; SPOT5 panchromatic images of 5 m resolution coupled with a freely and globally available DEM. The method takes advantage of multi-temporal images to detect changes based on radiometric variations after precise coregistration/orthorectification. Removal of false alarms is then undertaken using shape, orientation and radiometric properties of connected pixels defining objects. 80% of the landslides and 93% of the landslide area are detected indicating small omission errors but 50% of false alarms remain. They are removed using expert based analysis of the inventory. The method is applied to realize the first comprehensive inventory of landslides triggered by the Pisco earthquake (Peru, 15/08/2007, Mw 8.0) over an area of 27,000 km2. 866 landslides larger than 100 m2 are detected covering a total area of 1.29 km2. The area/number distribution follows a power-law with an exponent of 1.63, showing a very particular regime of triggering in this arid environment compared to other areas in the world. This specific triggering can be explained by the little soil cover in the coastal and forearc regions of Peru. Analysis of this database finally shows a major control of the topography (both orientation and inclination) on the repartition of the Pisco-triggered landslides. © 2013 by the authors.

News Article | February 23, 2017

VANCOUVER, BRITISH COLUMBIA--(Marketwired - Feb. 23, 2017) - Alianza Minerals Ltd. (TSX VENTURE:ANZ) ("Alianza" or the "Company") announces that an application has been made with the Peruvian authorities (INGEMMET - Instituto Geologico Minero y Metalúrgico) for nine concessions comprising six properties in central Peru. These new properties target base metals mineralization in the Peruvian Polymetallic Belt, a prolific region host to deposits such as the Cerro de Pasco Mine, where zinc, lead and copper ore has been mined for over 100 years. Alianza's target properties were internally generated from a study that examined a range of criteria including metallogeny, regional geology, regional structure, private and public geochemical databases, favourable CSR conditions and local knowledge. Management is planning reconnaissance exploration programs for all six of these properties once the concession grants are completed. It is anticipated that this process will be completed in Q2 2017 and reconnaissance work will commence shortly thereafter. "Alianza is acquiring these new concessions as a result of in-house generative work that identified 30 grassroots targets," stated Jason Weber, P.Geo., President and CEO of Alianza. "We are targeting large base metal deposits and this region of Peru is known for its lead and zinc production, with mines that were first developed over one hundred years ago. We are eager to visit these targets and ground-truth our ideas." Alianza's financing announced on February 15, 2017 has been increased to $625,000 for a total of 5,000,000 units. The units have also been amended to include one common share and one half common share purchase warrant valid for a three year period and now exercisable at $0.20 per share. The financing is fully subscribed and will close within 10 days. Alianza increases the chances of success in mineral exploration by using the "Prospect Generator" business model, focussing on gold and copper exploration in Latin America and Nevada. The Company has 28.3 million shares issued and outstanding, and is listed on the TSX Venture Exchange (TSX VENTURE:ANZ). Mr. Jason Weber, BSc, P.Geo., Alianza's President and CEO is a Qualified Person as defined by National Instrument 43-101. Mr. Weber supervised the preparation of the technical information contained in this release. NEITHER THE TSX VENTURE EXCHANGE NOR ITS REGULATION SERVICES PROVIDER (AS THAT TERM IS DEFINED IN THE POLICIES OF THE TSX VENTURE EXCHANGE) ACCEPTS RESPONSIBILITY FOR THE ADEQUACY OR ACCURACY OF THIS RELEASE. STATEMENTS IN THIS NEWS RELEASE, OTHER THAN PURELY HISTORICAL INFORMATION, INCLUDING STATEMENTS RELATING TO THE COMPANY'S FUTURE PLANS AND OBJECTIVES OR EXPECTED RESULTS, MAY INCLUDE FORWARD-LOOKING STATEMENTS. FORWARD-LOOKING STATEMENTS ARE BASED ON NUMEROUS ASSUMPTIONS AND ARE SUBJECT TO ALL OF THE RISKS AND UNCERTAINTIES INHERENT IN RESOURCE EXPLORATION AND DEVELOPMENT. AS A RESULT, ACTUAL RESULTS MAY VARY MATERIALLY FROM THOSE DESCRIBED IN THE FORWARD-LOOKING STATEMENTS.

Rivera M.,INGEMMET | Rivera M.,CNRS Magmas and Volcanoes Laboratory | Thouret J.-C.,CNRS Magmas and Volcanoes Laboratory | Marino J.,INGEMMET | And 2 more authors.
Journal of Volcanology and Geothermal Research | Year: 2010

Ubinas volcano is located 75km East of Arequipa and ca. 5000 people are living within 12km from the summit. This composite cone is considered the most active volcano in southern Peru owing to its 24 low to moderate magnitude (VEI 1-3) eruptions in the past 500years. The onset of the most recent eruptive episode occurred on 27 March 2006, following 8months of heightened fumarolic activity. Vulcanian explosions occurred between 14 April 2006 and September 2007, at a time ejecting blocks up to 40cm in diameter to distances of 2km. Ash columns commonly rose to 3.5km above the caldera rim and dispersed fine ash and aerosols to distances of 80km between April 2006 and April 2007. Until April 2007, the total volume of ash was estimated at 0.004km3, suggesting that the volume of fresh magma was small. Ash fallout has affected residents, livestock, water supplies, and crop cultivation within an area of ca 100km2 around the volcano. Continuous degassing and intermittent mild vulcanian explosions lasted until the end of 2008. Shortly after the initial explosions on mid April 2006 that spread ash fallout within 7 km of the volcano, an integrated Scientific Committee including three Peruvian institutes affiliated to the Regional Committee of Civil Defense for Moquegua, aided by members of the international cooperation, worked together to: i) elaborate and publish volcanic hazard maps; ii) inform and educate the population; and iii) advise regional authorities in regard to the management of the volcanic crisis and the preparation of contingency plans. Although the 2006-2008 volcanic crisis has been moderate, its management has been a difficult task even though less than 5000 people now live around the Ubinas volcano. However, the successful management has provided experience and skills to the scientific community. This volcanic crisis was not the first one that Peru has experienced but the 2006-2008 experience is the first long-lasting crisis that the Peruvian civil authorities have had to cope with, including attempts to utilize a new alert-level scheme and communications system, and the successful evacuation of 1150 people. Lessons learned can be applied to future volcanic crises in southern Peru, particularly in the case of reawakening of El Misti volcano nearby Arequipa. © 2010.

News Article | November 21, 2016

Perú Sabancaya has been restless for the last two years, with periods of heightened activity and a return to quiet. However, it looks like the Peruvian volcano has entered a new phase of activity since early November. The volcano has produced dozens of explosive eruptions since November 6, when the renewed activity began. This first explosion generated an M3.6 earthquake as well. Ash has reached 1.5-3.5 kilometers (4,900-11,400 feet) over the volcano and spread ash over 40 kilometers (25 miles) from the volcano on the people living across the area. The ash plumes (see below) have been some of the highest ever recorded at Sabancaya and video from the explosions show a vigorous plume of dark grey ash from the volcano. Interestingly, the number of earthquakes is down some from late September and early October, possibly betraying the time for the magma to rise from depth into the volcano to cause these explosions. Deformation of the volcano continues, which supports the idea that magma is still rising into the edifice and sulfur dioxide emissions remain high (almost 3,000 tonnes/day), so all signs still point to continued likelihood of explosive eruptions. This continued threat means that a state of emergency has been declared across 23 districts around Sabancaya due to this ash hazard for the next 60 days. This area is a tourist destination, so any prolonged unrest at Sabancaya could impact that industry. The volcano remains on Yellow alert status. You can see the changing activity at Sabancaya on the webcam pointed at the crater. Sabancaya isn’t the only restless volcano in Peru right now, either. Ticsani has been experiencing earthquakes over the past few months that all suggest magma is moving into the volcano. The number of earthquakes has dropped some at Ticsani since earlier in the year, but harmonic tremor, a sure sign of magma movement, has increased over the past few weeks. However, deformation and degassing is low, so an eruption isn’t likely happening in the immediate future. The only known eruption of Ticsani was in ~1800 A.D. Ubinás has also had an eventful 2016, with numerous explosions from Peru’s most active volcano. Over the past few months, the volcano has had a couple bouts of seismicity that quieted during much of October. However, since the start of November, there have been numerous earthquakes, tremor and some explosions that sent ash ~1.5 km (4,900 feet) over the volcano. Those explosions coincided with a spike in sulfur dioxide emissions, all supporting the conclusions that new magma is rising into the volcano. You can check out the IGP webcam or INGEMMET webcam to see what’s going on at the restless Andean volcano. Further south, an explosive eruption on November 17 occurred at Nevados de Chillán that sent ash 1.2 kilometers (3,900 feet) over the volcano. This is one of a number of “ash puffs” that the volcano has produced over the last year, most of which were noticed thanks to the webcam pointed at the volcano. Nevados de Chillán remains at Yellow alert status. Meanwhile, M3.6 earthquake shook Hudson in southern Chile. The SERNAGEOMIN thinks the earthquake was related to fluid movement within the volcano, although it could be from hydrothermal activity rather than magma. The last eruption from Hudson was in 2011 and the 1991 eruption was a VEI 5, one of the largest of the 20th century.

Roperch P.,IRD | Carlotto V.,INGEMMET | Chauvin A.,Gosciences Rennes
Tectonics | Year: 2010

We report a combined study of anisotropy of low field magnetic susceptibility (AMS) and paleomagnetism from 16 sites in a sedimentary sequence of Eocene-early Oligocene red beds in southern Peru. Incipient tectonic strain is recorded during the early stages of deformation. Nonhorizontal magnetic lineation in geographic coordinate suggests either noncylindrical folding and/or interference of two phases of compressive deformation and tectonic rotation. Applying the classic tilt correction results in significant dispersion in paleomagnetic declinations and apparent clockwise and counterclockwise relative tectonic rotations. A dispersion in the orientation of the magnetic lineation also arises from a simple classic tilt correction inducing apparent local rotation in paleostress determination. The magnetic lineation is a good proxy to detect a complex history of folding when the finite strain is not large enough to reset the magnetic fabric acquired during the early stages of deformation and when detailed geological field mapping is not available or not possible. In the present study, a double correction rotating first the lineation to the horizontal reduces significantly the dispersion of the paleomagnetic data with respect to conventional tilt correction (Fisher parameter k increases from 14 to 35). The interest of this double correction must obviously be evaluated for each study according to the complexity of the folding and the intensity of the deformation. Assuming a mean age of 40 Ma for the sedimentary sequence, no significant rotation (-4.5 8.4) is observed in this area of the Peruvian Andes. © 2010 by the American Geophysical Union.

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