IRTG-StRATEGy - Geodynamics

163-G 2.2

henry.wichura — Thu, 16 Jun 2016 15:57:50 +0000

Multiple basin filling and excavation cycles and fault reactivation

Working Package:

Temporal Process:

Prof. Manfred Strecker, Ph.D.Potsdam University Prof. Dr. Ricardo AlonsoSalta University (ARG)Prof. Dr. Fernando HongnSalta University (ARG)

163-G 4.2

Anonymous — Fri, 25 Sep 2015 10:17:20 +0000

10|2018 – 09|2021

Magmatic-hydrothermal processes forming epithermal Sn-Ag ore deposits in NW Argentina

M.Sc. Malte StoltnowGFZ Potsdam P.D. Dr. Philipp WeisGFZ Potsdam Dr. Volker LüdersGFZ Potsdam apl. Prof. Dr. Uwe AltenbergerPotsdam University Dr. Robert TrumbullGFZ Potsdam Prof. Dr. Pablo CaffeJujuy National University (ARG)Raúl Becchio, Ph.D.Salta National University (ARG)Dr. Marcelo ArnosioSalta University (ARG)

The Puna Plateau in NW Argentina hosts a variety of economic Sn-Ag and Ag deposits which are believed to be analogues to the polymetallic epithermal deposits of the southern Bolivian Sn belt. However, while the Bolivian deposits have a clear association to Miocene magmatism, a direct connection to magmatic intrusions is lacking for the Argentinian deposits so far. Recent studies of fluid inclusions hosted in quartz and ore minerals from the giant Pirquitas deposit have revealed compelling evidence that the hydrothermal system was characterized by mixing of magmatic fluids and meteoric water. In the follow-up PhD project, we will extend fluid inclusion studies to new deep wells in the area of the Pirquitas deposit and to the Cinchillas deposit, which is also located in the Puna Plateau but has a different style of Ag mineralization. The PhD candidate will perform geochemical studies of Pb and S isotopic compositions and fluid inclusions in ore and gangue minerals (microthermometry, Raman spectroscopy, LA-ICPMS, noble gas isotopes). In addition, the candidate will use numerical modelling to resolve the magmatic-hydrothermal transition from an inferred porphyry system at depth to the epithermal regime at shallower levels, using the constraints obtained from data of the Pirquitas system.

10|2015 – 09|2018

Magmatic and hydrothermal processes in the Andean Cu-Au and Sn-Ag ore belts of NW Argentina

The Cenozoic central Andes host orogen-parallel belts of magmatic-related ore deposits with contrasting metal associations (Fe, Cu-Au, vs. polymetallic, Sn-Ag). This project will investigate the role of magmas vs. hydrothermal fluids in metal transport and metallogenesis. There a close linkages to projects G3.5 and G4.1. Besides the potential role of magma processes (differentiation, fluid saturation), other important factors to be studied are the roles of local basement composition and deformation for the metal enrichment, transport, and deposition (faults and shear zones – link to project 10). Both belts are located in an E-W region of 70-km width, and the mineralization and magmatism belong to the main metallogenic epoch in the S central Andes (12-15 Ma), so the geodynamic scenario can be considered invariable. We hypothesize that the different metal associations are controlled by different magma compositions, which depend on source characteristics in addition to the conditions of magma genesis and differentiation, especially oxygen fugacity and volatile contents. To test the roles of magma composition and hydrothermal fluids, the PhD candidate will combine standard geochemistry and petrology of ore and wall rocks with fluid-inclusion studies, melt inclusions and ore minerals with SIMS ion probe analysis, Raman spectroscopy, LA-ICPMS, IR microthermometry, and stable gas isotopes.

Working Package:

WP4 - Georesources

Temporal Process:

Intermediate

Dr. Louis DesanoisGFZ Potsdam Dr. Robert TrumbullGFZ Potsdam Dr. Volker LüdersGFZ Potsdam apl. Prof. Dr. Uwe AltenbergerPotsdam University Raúl Becchio, Ph.D.Salta National University (ARG)Prof. Dr. Pablo CaffeJujuy National University (ARG)

163-G 4.1

Anonymous — Fri, 25 Sep 2015 10:16:27 +0000

10|2018 – 09|2021

Magmatic processes, fluid-rock interaction and provenance of Nb-Ta and REE mineralizations in NW Argentina

M.Sc. Enrico RibackiUniversity of Potsdam apl. Prof. Dr. Uwe AltenbergerPotsdam University Dr. Robert TrumbullGFZ Potsdam Dr. Volker LüdersGFZ Potsdam Prof. Dr. Monica López de LuchiBuenos Aires University (ARG)Dr. Raúl LiraMuseum of Mineralogy Córdoba (ARG)Dr. Clara CisternaTucumán University (ARG)Dr. José Pablo LopezTucumán University (ARG)Raúl Becchio, Ph.D.Salta National University (ARG)

Deep-seated processes in the Andean crust, now exposed by tectonics and erosion in the foreland, are integral parts of the resource-forming systems under investigation. After recycling of continental crust by partial melting and magmatism, hydrothermal fluids of magmatic and/or meteoric origin are key agents for a range of processes that form and modify metallic ore deposits. This project will investigate a range of granite-pegmatite related rare earth element (REE) and Sn-Ta-Nb-Li mineralization types in the San Luis range of NW Argentina. The goals are to assess the relative influence of magma composition, particularly the S-type vs. A-type granite composition, in the metals enrichment, and to determine the role of fluids in mineralization. We will concentrate on well-characterised metamorphic complexes and their intruding granitoids of the San-Luis range (Eastern Sierras Pampeanas), where compositionally distinct pegmatites occur: predominantly intragranitic mostly Ordovician Nb-Y-F pegmatites related to water-poor and fluorine-rich melts and mostly Ordovician Li-Cs-Ta pegmatites related to water-rich peraluminous melts and emplaced either in the metamorphic complexes or in their intruding granitoids. These will be compared with similar occurrences further north in Sierras Pampeanas. A small but significant part of the work will follow the alteration of the NYF pegmatites to obtain proxies for provenance studies of critical elements (source to sink) and the research will also help constraining the sources of granite magmas and the role of the interplaying between recycling of continental crust and juvenile additions.

10|2015 – 09|2018

Provenance and transport of Sn (Nb-Ta) and REE from the pre-Andean crustal basement: primary mineralization and secondary enrichment processes

This project will investigate the primary source rocks for Sn (and Nb-Ta) and rare earth elements (REE) in the pre-Andean basement rocks (granites, pegmatites, metamorphic complexes) and the enrichment/mobilization processes related to chemical (hydrothermal alteration or weathering) and mechanical processes (ductile or brittle deformation in fractures and ductile shear zones). The investigation will focus on selected field occurrences of Palaeozoic granites, pegmatites, and their highly deformed metamorphic equivalents of the pre-Andean crustal basement, especially of the Salta Province. For the REE minerals especially (carbonates, phosphates, fluor-carbonates, oxides), there is substantial redistribution related to solubility-reprecipitation processes in the deep crust (e.g. lode deposits in shear zones) as well as surface adsorption in weathered exposures (e.g. heavy REE enrichment in clays: Longnan-type deposits). Because tin minerals and coltan (Nb-Ta ore) from pegmatite fields are commonly mined in alluvium (placers), it is critically important to understand how secondary processes (alteration, chemical and mechanical weathering) affect the criteria used for provenance identification. Therefore, the major aim of the project will be to analyse the origin and enrichment processes of the rare elements in primary (magmatic) as well as in secondary (fluid- and structurally controlled) environments. Emphasis will fall on studies in Salta province, because of the geological situation, including rare element pegmatites, and the direct links with project [G 2.2] working on the reactivation of fault zones and project [G 3.5], which addresses the role of basement composition for metal enrichment in near-surface volcano-tectonic complexes. Close collaboration with project [G 4.2] and the Argentine metallogenesis projects will extend the scope of investigation to places best suited to study the relevant processes (e.g., shear zones, alteration/weathering profiles, etc.). The research will combine modern techniques of mineralogical, microstructural and (isotope) geochemical analysis with field campaigns to examine key localities best suited to study the chemical and mechanical alteration of primary mineralization. The relevance of this study is in the field of mineral exploration primarily, i.e., for orogenic structurally-controlled REE deposits, and also for the growing field of provenance certification to control conflict ores.

Working Package:

WP4 - Georesources

Temporal Process:

Long Term

M.Sc. Melanie LorenzPotsdam University apl. Prof. Dr. Uwe AltenbergerPotsdam University Dr. Robert TrumbullGFZ Potsdam Prof. Dr. Roland OberhänsliPotsdam University Prof. Dr. Monica López de LuchiBuenos Aires University (ARG)Prof. Dr. Pablo CaffeJujuy National University (ARG)Raúl Becchio, Ph.D.Salta National University (ARG)

163-G 3.3

Anonymous — Fri, 25 Sep 2015 10:14:50 +0000

10|2018 – 09|2021

Lithospheric-scale 3D configuration of the Central Andes and adjacent forelands: constraints on along- and across-strike variations of density, temperature and strength

Lic. Constanza Rodriguez PicedaGFZ Potsdam Dr. Judith Bott (née Sippel)GFZ Potsdam Prof. Dr. Magdalena Scheck-WenderothGFZ Potsdam Prof. Dr. Claudia PrezziBuenos Aires University

There is a great variability in observed crustal deformation style and intensity from the subduction trench across the highest Andes to the foreland lows as well as from the Northern to the Southern Central Andes. Beside the subducting plate that exerts important controls on deformation through its (spatially and temporally) varying dynamics, it is the intrinsic physical properties of the overriding plate that govern the formation of zones of crustal strength and weakness. With this project we want to explore the present-day compositional, thermal and rheological configuration of the Central Andes and adjacent forelands on a lithospheric scale by means of data-driven 3D numerical models. While in the first project phase of StRATEGy this work package focused on the Northern Central Andes, this follow-up project will investigate lithological and related physical heterogeneities of the sediments, the crystalline crust, and the mantle of the Southern Central Andes. For this purpose, geological and geophysical observations such as seismic, seismological, gravity and thermal data will be integrated into consistent 3D models. These static models will be useful to constrain numerical thermo-mechanical experiments (such as planned in project G 3.2) that explore the stress-and-strain relationships across the entire subduction system.

10|2015 – 09|2018

3D lithosphere-scale density and thermal structure of the Central Andean foreland basins

Since the late Oligocene, the intracontinental Chaco-Paraná basin system evolved contemporaneously with the adjacent Andean fold-and-thrust belt. Consequently, four characteristic foreland depozones with different sediment thickness have developed, including (from west to east) wedge-top, foredeep, forebulge, and backbulge depositional environments. In places, very young sedimentary sequences directly overlie basement rocks in the E, while toward the orogen, they cover several kilometres of Paleozoic and Mesozoic sediments. Geophysical data provides local information on the depth to the Moho and the lithosphere-asthenosphere-boundary (LAB); accordingly, the crust and lithosphere thin from ~43 km and ~120 km in the north-eastern parts of the Chaco-Paraná basin to ~35 km and ~80 km, respectively, in the central parts. Towards the Andean orogen in the west, crustal thicknesses increase to more than 60 km and the LAB deepens to more than 150 km. Despite the abundance of geological and geophysical data, there is currently no regionally consistent 3-dimensional representation of the entire lithosphere in the region. Such a model depicting the main compositional heterogeneities of the sediments, the crystalline basement, and the lithospheric mantle has recently been developed for the Central Andes and will be critical for unraveling the long-term evolution of the foreland basin. Based on geological maps, well-logs, and seismic data made available to StRATEGy from industry and our Argentine partner E. Rossello, regional thickness variations of main tectonostratigraphic units will be integrated in a 3D structural model in the framework of PhD project. Subsidence rates and spatiotemporal shifts of depocentres will be cast in terms of phases of increased Andean tectonic loading. The models developed in this project will provide boundary conditions for petroleum-potential assessment in project [G 3.1] and a regional tectonic framework for project [G 3.4]. Furthermore, these models will allow rheological heterogeneities to be distinguished, particularly crustal zones of mechanical weakness, representing important constraints for large-scale numerical thermo-mechanical models developed in projects [G 3.2].

Working Package:

WP3 - Basin Modeling

Temporal Process:

Long Term

Intermediate

Dr. Christian MeeßenGFZ Potsdam Dr. Judith Bott (née Sippel)GFZ Potsdam Prof. Dr. Magdalena Scheck-WenderothGFZ Potsdam Prof. Dr. Claudia PrezziBuenos Aires University

163-G 3.2

Anonymous — Fri, 25 Sep 2015 10:14:10 +0000

10|2018 – 09|2021

The nature of the North-South change of the magnitude of tectonic shortening in Central Andes at Altiplano-Puna latitudes: a thermomechanical modeling approach

Prof. Dr. Stephan SobolevGFZ Potsdam Dr. Andrey BabeykoGFZ Potsdam Prof. Dr. Laura GiambiagiCuyo National University (ARG)M.Sc. Michaël PonsGFZ Potsdam

The first order features of the Central Andes tectonics are change of tectonic styles and magnitude of tectonic shortening from Altiplano to Puna latitudes. While causes of the change of tectonic styles were successfully investigated by comprehensive thermomechanical modeling in the first phase of the [G 3.2] StRATEGy project, the cause of change of shortening magnitude remains poorly understood. Our working hypothesis is that difference in strength of the upper plate that caused difference in tectonic styles also resulted in different rates of trench roll-back. To test this hypothesis and investigate other possibilities, in the new phase of the project we intend to extend our current models to the west including subducting Nazca plate. This will require more than doubling of the modeling area. We will build our models using experience of the first project phase and as previously will first run high-resolution 2D models along the Altiplano and Puna cross-sections and finally full 3D model including the entire region. To do that we will incorporate the updated versions of 3D thermomechanical codes LAMEM and ASPECT and 3D model of the lithospheric structure in the Central Andes developed in the partner project [G 3.3] and its extension.

10|2015 – 09|2018

Controls of Cenozoic foreland-deformation patterns

The Andean foreland demonstrates a pronounced N-S oriented differentiation in the style and magnitude of deformation and the nature of sedimentary basins. East of the Altiplano-Puna plateau and the Eastern Cordillera, a wedge-shaped, ~250-km-wide thin-skinned fold-and-thrust belt defines the eastern border of the orogen, which then transitions into the contiguous Chaco-Paraná foredeep. The spatial extent of the fold-and-thrust belt in Bolivia correlates with thick Paleozoic units, in which a series of Silurian, Devonian, and Carboniferous detachments define the basal decollément of the orogenic wedge. However, south of approximately 24°S, these mechanically weak layers thin and eventually disappear, and the thin-skinned style of deformation is replaced by the thick-skinned deformation of Santa Barbara and Sierras Pampeanas broken forelands. The gradual increase of the wavelength of foreland structures from north to south is accompanied by a decrease in accumulated shortening, a decrease in the width of orogenic plateau, and increasing lithospheric temperature. North-south trends are also evident in other key aspects of the South Central Andes, such as the N-S directed passage of Juán Fernandez Ridge during last 26 Ma and the widening of the magmatic arc and the start of an ignimbrite flare-up in the Puna. These observations suggest intimate relationships between style and intensity of deformation involving both shallow and deep lithospheric structures and processes. Supported by the results of numerous field observations, large-scale numerical thermomechanical modeling provides a valuable tool for testing geological and geodynamical hypotheses that are built on the apparent correlations between the different phenomena observed in the Central Andes. Previous 2D-models of the Central Andes already attempted to quantify some of these correlations. Recent progress in numerical modeling techniques, however, allows for an extension of this research towards 2.5- and 3D-lithospheric models. We will study the Andes from ca. 18 to 35°S, integrating the characteristics of the Nazca plate and the Andean foreland. Our numerical modeling will incorporate spatially varying age and geometry of the Nazca plate and thickness of the overriding South American plate to better constrain interplate stress transfer. Both deep and shallow model geometries and structures will be constrained by new data gathered in the framework of this initiative. Our project is tightly coupled with two other modeling projects: [G 3.3] on the 3D structural and thermal reconstruction of the evolution of the Chaco-Paraná Basin. The two projects, which cover somewhat different scales and/or locations, will exchange their input data and results, thus providing valuable constraints for each individual effort. Other important regional constraints are expected from field-studies planned in project [G 3.4], aimed at revealing long-term controls of sedimentary basin architecture in the brokenforeland realm.

Working Package:

WP3 - Basin Modeling

Temporal Process:

Long Term

Dr. Sibiao LiuGFZ Potsdam Prof. Dr. Stephan SobolevGFZ Potsdam Dr. Andrey BabeykoGFZ Potsdam Dr. Javier QuinterosGFZ Potsdam apl. Prof. Dr. Frank KrügerPotsdam University Dr. José MescuaMendoza University Prof. Dr. Laura GiambiagiCuyo National University (ARG)

163-G 2.1

Anonymous — Fri, 25 Sep 2015 10:11:09 +0000

10|2018 – 09|2021

Quaternary landscape evolution Paleoseismology and active tectonics of the NW-Argentineian broken foreland under the influence of tectonic processes.

M.Sc. Gregor Lauer-DünkelbergPotsdam University Prof. Manfred Strecker, Ph.D.Potsdam University Prof. Dr. Fernando HongnSalta University (ARG)Dr. Carolina Montero LopezIBIGEO Conicet

Fault systems in the broken foreland of NW Argentina are associated with isolated seismicity, deformation, and uplift, and they pose a major problem in understanding the spatiotemporal characteristics of individual earthquakes and long-term deformation patterns. Range uplift in these environments is highly disparate in time and space, without a clear deformation front as in the foreland fold-and-thrust belt to the north. Some ranges constitute large anticlines that have formed over blind thrusts, such as the growing anticlines west of the town of Salta.

On geological time scales, the erratic tectonic behavior of fault-bounded intermontane basins has caused a disturbance of the fluvial systems and resulted in multiple episodes of basin filling and sediment removal to the foreland. Importantly, there appears to be a relationship between sediment removal and ensuing changes in crustal stresses in these environments. For example, fault reactivation within and along basin margins is observed to follow the removal of the sedimentary load on time scales of several 105 years.

To elucidate the mechanisms by which such fault arrays in broken forelands organize, activate, and deactivate over time, we will compare geomorphic and geologic records that integrate the activity of faults over multithousand-year timescales (i.e., by dating deformed geomorphic features such as fans and terraces using U/Pb dating) to million-year timescales (i.e., by applying geochronologic and thermochronologic methods). These types of observations will enable the determination of the spatiotemporal faulting history and help to assess how deformation may be transferred between fault fault systems over long timescales (PhD1). We will furthermore use the Gale geodynamic model 87 to study how topographic construction and changing constitutive properties of fault zones may moderate the transfer of deformation between such arrays (PhD2).

As deformation accrues and mountain ranges are built, body forces in the crust may cause one set of structures to become less susceptible to failure relative to surrounding structures. Deformation may then systematically migrate from areas of higher to lower elevations. However, coeval erosional processes export mass from the basins and ranges, and so may buffer the accumulation of body forces in the crust. Gale allows application of surface-processes rules, enabling us to couple erosion at the surface to changes in the deformation field within the upper crust. Combining field observations, geochronology and modeling is expected to help us ascertain plausible causal mechanisms of spatiotemporal patterns of deformation.

10|2015 – 09|2018

Spatiotemporal characteristics of paleo-, historic and recent earthquakes in the broken foreland of the south-central Andes

In this project we will investigate large and medium-magnitude earthquakes using waveform analysis of historical and modern seismograms for event location, magnitude, and depth as well as focal mechanisms and source-time function. Historical earthquakes recorded at analog stations worldwide (primarily recorded on paper or film) since the beginning of the last century can be digitized and analyzed with advanced methods to better constrain their characteristics. For example, using waveform inversion, we are able to derive depth, lateral extent, and the true fault plane as well as zones of increased slip along rupture planes. With such a data set, we aim to identify and quantify the related earthquake surface-rupture trace or remnants of earlier surface ruptures in the epicentral regions. High-resolution satellite imagery, aerial photography, cosmogenic nuclide exposure dating of offset geomorphic markers, fault scarp measurements, and fault trenching will complement this analysis and provide an unprecedented data set to assess earthquake characteristics. We will focus on the large magnitude, shallow crustal seismic events in the region in the Andean foreland, e.g., the 1894 (M8), 1908 (M6.8), 1929 (M6.5), 1944 (M7.8), 1952 (M7.0) and 1977 (M7.4) events. Depending on the quality of historic records and local conditions, we will select two sites (preferably the 1894 and 1952/1977 San Juan events). For these sites, we will relocate medium-size earthquakes, determine their seismic moment tensors (focal mechanisms) and depth from waveform inversion and thereby test possible relationships between recent seismic activity and surficial deformation characteristics. Deployment of temporary seismic stations in addition to existing permanent stations at one or two selected sites will help identify active structures from small magnitude events. We will reevaluate seismic-moment tensors for the foreland region for recent events, where the magnitude threshold depends on data availability. Taken together, the results will provide better insight into the relationships between aseismic and seismic deformation, the identification of active structures, and possible changes in the spatiotemporal deformation characteristics of important structures. Such knowledge will ultimately shed light on the dynamics of Quaternary tectonic activity compared to the overall tectonic and topographic evolution of ranges in the broken foreland and help elucidate the background sedimentation rates and patterns in light of tectonic forcing mechanisms.

Working Package:

WP2 - Tectonics

Temporal Process:

Short Term

Dr. Martin ZeckraPotsdam University apl. Prof. Dr. Frank KrügerPotsdam University Prof. Dr. Fernando HongnSalta University (ARG)Dr. Patricia AlvaradoSan Juan University (ARG)