A. P. Willner

• Prof. Dr.
• Professor at Ruhr University Bochum

New analytical and field techniques, as well as increased international communication and collaboration, have resulted in significant new geological discoveries within the Appalachian-Caledonian-Variscan orogen. Cross-Atlantic correlations are more tightly constrained and the database that helps us understand the origins of Gondwanan terranes conti...

We present a numerical modeling approach to infer timescales of the exhumation and cooling history recorded in the chemical composition of minerals in a garnet pyroxenite from the Granulitgebirge, Saxony/Germany. The studied sample contains remarkable exsolution textures from former megacrysts that produced up to millimeter-wide, alternating lamell...

Detrital zircon populations in sedimentary rocks from the Laurentian margin and the accreted microcontinent Ganderia on both sides of the main Iapetus suture (Red Indian Line) in central Newfoundland have been studied by combined U-Pb and Lu-Hf isotope analyses. Variation in epsilon Hf-(t) values with age of zircon populations of distal provenance...

Laser ablation inductively coupled plasma mass spectrometry U–Pb and Lu–Hf isotope analyses of detrital zircon from Neoproterozoic–Cambrian clastic sedimentary rocks in the Mira terrane (Cape Breton Island, Nova Scotia, Canada; West Avalonia) and the Stavelot–Venn Massif (East Belgium; East Avalonia) support deposition on an originally coherent mic...

To better understand geodynamic processes related to the assembly of various belts of volcanic-sedimentary rocks in the Avalonian Mira terrane of SE Cape Breton Island (protolith ages 680-60 Ma) we investigated metamorphic processes in 20 white-mica-bearing mafic and felsic metavolcanic rocks. The felsic metavolcanic rocks are foliated and partly s...

Detrital zircon populations in precollisional sediments from the Laurentian margin and the accreted Ganderia microplate have been studied on both sides of the main Iapetus suture (Red Indian Line) in central Newfoundland. Characteristic detrital zircon Hf isotopic signatures (ɛHf(t)) reflect the large-scale crustal evolution of the source continent...

In the late Palaeozoic fore-arc system of north-central Chile at latitudes 31–32°S (from the west to the east) three lithotectonic units are telescoped within a short distance by a Mesozoic strike-slip event (derived peak P–T conditions in brackets): (1) the basally accreted Choapa Metamorphic Complex (CMC; 350–430°C, 6–9 kbar), (2) the frontally a...

We describe the geometry and kinematics of a Jurassic to Early Cretaceous transpressive sinistral strike-slip system within a metamorphic basement inlier of the Mesozoic magmatic arc near Bahia Agua Dulce at latitudes 31–32°S in north-central Chile and discuss possible relations with the Atacama Fault System further north. Sinistral transpression o...

Ancient arc-continent collisions are commonly informally described as hard or soft, although the differences between these two are rarely defined. We define a hard collision where the overriding arc (including infant arcs preserved in obducted ophiolites) has been significantly thickened in proximity to the suture zone due to internal deformation....

The Guarguaraz Complex in West Argentina formed during collision between the microplate Chilenia and South America. It is composed of neritic clastic metasediments with intercalations of metabasic and ultrabasic rocks of oceanic origin. Prograde garnet growth in metapelite and metabasite occurred between 1.2 GPa, 470°C and 1.4 GPa, 530°C, when the...

Sodic pyroxene is reported from an Ordovician metatrachyte of the Kaczawa Mountains, SW Poland. Its composition ranges from Jd 0.98 Ae 0.02 to Jd 0.15 Ae 0.85 . Relict jadeite and phengite (up to 3.75 Si atoms per fomula unit) belong to the peak-pressure assemblage of an early H P -L T event. Later greenschist-facies stages are represented by riebe...

Rare earth element (REE) concentrations of ultrahigh-pressure (UHP) metamorphic rocks from the Dora-Maira Massif as well as of their granitic country rocks were investigated to evaluate their primary relationships. Additionally, retrograde derivatives of these rocks and mineral separates of pyrope, phengite, and monazite from 'pyrope quartzite' wer...

The Madre de Dios Metamorphic Complex (MDMC) in southern Chile is a fossil frontal accretionary prism, which is mainly composed of metapsammopelitic rocks, intercalations of oceanic rocks (greenstone and metachert) and platform carbonate. We concentrated on the metabasite to decipher the metamorphic evolution. This rock type contains assemblages of...

Along the Coastal Cordillera of Chile between the latitudes 30° and 55°S fossil accretionary systems have been developed at the passive margin of the microplate "Chilenia" after its collision with the western Gondwana margin. This evolution started in late Palaeozoic times in the north and during Mesozoic times in southern Chile. The areas of fossi...

In the Coastal Cordillera of central Chile a coherently preserved architecture of a late Paleozoic accretio- nary prism is exposed at 36°-35°S in close spatial association with a neighbouring area at 34°-35°S, where it is strongly modifi ed by post-accretional processes. Syn- and post-accretional structures can be distinguished relatively easily in...

Pseudosections for two sediments and one basalt calculated in the system K2O–Na2O–CaO–MgO–FeO–Fe2O3–Al2O3–TiO2–SiO2–H2O for the P–T range 10 to 35 kbar, 300 to 900°C give useful insights into the amount of H2O released from oceanic crust in subduction zones. In cold subduction zones (20 kbar–300°C to 35 kbar–500°C) hydrous minerals storing 3 to 4 w...

At the Pacific convergent margin of South America around the latitude 35° S two fundamental types of accretionary systems occur: (1) the Paleozoic collisional accretionary prism of the Guarguaraz Complex at the suture between the Cuyania and Chilenia microplates in W Argentina (longitude 69° W) and (2) the late Paleozoic coastal accretionary comple...

P-T pseudosections were calculated in the system Na-Ca-K-Fe-Mg-Al-Si-Ti-H-O with the PERPLE_X software package for the pressure-temperature range 1-25 kbar and 150-450 degrees C to gain a better understanding of the phase relations and the dehydration behaviour of psammopelite and mid-ocean ridge basalt (MORB) during prograde metamorphism at very-l...

Detrital zircon provides a powerful archive of continental growth and recycling processes. We have tested this by a combined laser ablation ICP-MS U–Pb and Lu–Hf analysis of homogeneous growth domains in detrital zircon from late Paleozoic coastal accretionary systems in central Chile and the collisional Guarguaráz Complex in W Argentina. Because d...

Thermodynamic calculations have been undertaken in the system Na-Ca-K-Fe-Mg-Al-Si-Ti-H-O with the PERPLE_X software package (Connolly, 1990 and updates) for a better understanding of the dehydration behavior of metapelites and metabasites during prograde metamorphism. To obtain reasonable results for the temperature range 150-450° C at pressures up...

We use a coupled petrological–thermomechanical model of subduction with spontaneous slab bending to investigate magmatic productivity at active continental margins. The model is designed to simulate fossil Pacific-type margins that have a broad well-developed fore-arc accretionary wedge system. The degree of plate coupling strongly depends on the d...

Current geodynamic models of continental collision involving (ultra)high pressure complexes imply that even deeply subducted continental crust is significantly lighter than the ultrabasic upper mantle. To test this implication, we have investigated density changes of major components of continental crust, in particular metagreywacke and metapelite,...

Understanding the contact between the very low-grade metagreywacke of the Eastern Series and high-pressure metamorphosed schist of the Western Series in the Late Palaeozoic accretionary wedge of central Chile is fundamental for the understanding of the evolution of ancient accretionary wedges. We show the progressive development of structures and f...

We formulate a 2D coupled petrological-thermomechanical model of active continental margins. The model has been used to study the influence of different factors (e.g.: slab age, subduction rate, initial temperature distribution in the mantle wedge, strength of lithologies composing active margin) on spontaneous slab bending, aqueous fluid transport...

The Southern Urals of Russia contain what is arguably one of the best-preserved examples of an arc–continent collision in any Paleozoic orogen. The arc–continent collision history recorded in the rocks of the Southern Urals began in the Early Devonian with the onset of intra-oceanic subduction and the formation of the Magnitogorsk Arc and ended wit...

The Chilean accretionary wedge is part of a Late Paleozoic subduction complex that developed during subduction of the Pacific plate underneath South America. The wedge is commonly subdivided into a structurally lower Western Series and an upper Eastern Series. Understanding the contact between both series has been a long standing problem and is fun...

A multi-method geochronological approach is applied to unravel the dynamics of a paired metamorphic belt in the Coastal Cordillera of central Chile. This is represented by high-pressure–low-temperature rocks of an accretionary prism (Western Series), and a low-pressure–high-temperature overprint in the retro-wedge with less deformed metagreywackes...

In the Chilean Coastal Cordillera, two units, the Western and Eastern Series, constitute coeval parts of a Late Palaeozoic paired metamorphic belt dominated by siliciclastic metasediments. The Western Series also contains rocks from the upper oceanic crust and represents an accretionary prism. Omnipresent high-pressure conditions are reflected by N...

Within the metamorphic basement of the Coastal Cordillera of central Chile, the Western Series constitutes the high-pressure (HP)/low-temperature (LT) part (accretionary prism) of a fossil-paired metamorphic belt dominated by metagreywackes. In its eastern part, blocks derived from small lenses of garnet amphibolite with a blueschist facies overpri...

On Diego de Almagro Island in Chilean Patagonia (5130S), a convergent strike slip zone, the Seno Arcabuz shear zone, separates the Diego de Almagro Metamorphic Complex from very low grade metagreywackes in the east, which were intruded by Jurassic granitoids. The Diego de Almagro Metamorphic Complex is composed of a metapsammopelitic sequence conta...

Single grains of detrital white mica from two different synorogenic sediments in the Southern Urals were analysed using the insitu ultraviolet laser ablation Ar609 Ma age group is phengitic in composition (Si 3.3732 Ma age group is comprised of muscovite composition grains only. The first group is compatible with the time of late exhumation and emp...

Modeling of in situ rock properties based on a Gibbs free energy minimization approach shows that regional metamorphism of granulite facies may critically enhance the decrease of crustal density with depth. This leads to a gravitational instability of hot continental crust, resulting in regional doming and diapirism. Two types of crustal models hav...

Introduction Research on the geology of the Variscan belt of Central Europe has been under-taken for more than 200 years. Over this time, the theoretical knowledge about geodynamic processes continuously improved. Consequently, the introduction of concepts from material science into structural geology and a better understanding of geochronology and...

In the SW Urals a change of tectonic conditions occurred at around 620 Ma leading to a detrital input from contrasting provenance areas. Fifty-seven detrital zircons were separated from Proterozoic sandstones of this setting to study their typologies and pattern of U–Pb systematics.Detritus from Riphean sandstones (1.63–0.65 Ga) contains three popu...

1. Introduction During the last 2.5 decades our understanding of mass movements within the deep lithosphere improved substantially. The introduction of concepts from material science into geology in combination with a better understanding of phase petrology and isotope systems fundamentally changed the views on the tectonic evolution of many regio...

Extensive studies on HP and UHP metamorphic rocks exposed in collisional belts have shown that these rocks (1) are derived from both continental and oceanic crust, being intermingled on the length scale of typical tectonic nappes, (2) are frequently associated with hydrated peridotites, (3) reveal variable but systematically arrayed P-T-t records,...

Large-scale crustal thickening by tectonic and/or magmatic processes can lead to various complex patterns of multi-layered continental crust, It is well-known from one-dimensional thermal modeling that variations in total crustal thickness, mantle lithospheric thickness, thermal conductivities of the crust, and bulk radiogenic heat production of th...

The Bohemian Massif in the Central European Variscides contains many crustal slices with (ultra-)high-pressure rocks related to continent-continent collision. After closure of pre-existing oceans during the Devonian, excess crustal thickness was maintained for about 50 Ma until at around 340 Ma large volumes of high-pressure rocks from the crustal...

During collision of the East European Craton continental margin with the Magnitogorsk island arc in the Southern Urals, highly immature sandstones of the Zilair Formation (Famennian to Lower Tournaisian in age) were deposited on both sides of the Main Uralian fault (suture). An integrated study of the light and heavy mineral spectrum, as well as of...

Lenses of spessartine quartzites (coticules) are associated with greenschist intercalations in coastal exposures at Bahia Mansa within the mainly metapsammopelitic Western Series, which forms most of the basement in the Coastal Cordillera of central to southern Chile. The chemical compositions of the coticules can be explained by protoliths formed...

Petrological arguments show that regionally developed low- to medium-pressure, high-temperature granulite facies metamorphism may critically enhance the lowering of crustal density with depth. This leads to gravitational instability of homogeneously thickened continental crust, mainly due to changes in mineral assemblages and the thermal expansion...

Two contrasting provenance areas for Neoproterozoic sandstones can be distinguished in the southwestern Urals by light and heavy mineral analyses as well as by mineral chemistry. These reflect a dramatic change of geotectonic conditions at the eastern border of the Baltica protocontinent at around 610–620 Ma. Detritus from Riphean and Lower Vendian...

An integrated geological study of the tectono-metamorphic evolution of the metamorphic complex of Beloretzk (MCB) which is part of the eastern Bashkirian mega-anticlinorium (BMA), SW Urals, Russia shows that the main lithological units are Neoproterozoic (Riphean and Vendian age) siliciclastic to carbonate successions. Granitic, syenitic and mafic...

The high grade gneiss assemblage of central and southern Malawi belongs to the Neoproterozoic Mozambique belt of East Africa, and reached peak metamorphic conditions at 900 9 70°C and 9.5 9 1.5 kbar, followed by an isobaric cooling path. We report single zircon U–Pb and Pb–Pb ages and Nd isotopic data for orthogneisses and metapelites collected aro...

The Chonos Metamorphic Complex forms part of a belt of low-grade metamorphic rocks in the Chilean Coastal Cordillera that are interpreted as Palaeozoic–Mesozoic accretionary complexes. It comprises metapsammopelitic schists, metabasites and meta-ironstones occurring in two contrasting units. Special attention during microprobe study of key samples...

Zussmanite KFe 13 [AlSi 17 O 42 ](OH) 14 , a modulated 2:1 layer silicate, has so far been found only in iron-rich metasediments from Laytonville, California (Agrell et al. ), 1965). A new occurrence is reported here from Punta Nihue north of Valdivia, Chile, in banded stilpnomelane-schists. These are intercalated in the ‘Western Series’, a complex...

The Variscan Erzgebirge represents an antiform with a core of gneisses and mica schists, surrounded by a phyllitic mantle. The Gneiss-Eclogite Unit (GEU), in the central part, is a composite tectonometamorphic assemblage characterized by a HP-HT imprint and comprises migmatitic para- and orthogneisses, HT mylonites, HP granulites, eclogites and gar...

The Western Erzgebirge consists of a sequence of three tectonometamorphic nappe units with contrasting P-T histories that became juxtaposed during and after exhumation. From the tectonically lowermost to the uppermost these units are the Mica-Schist/Eclogite Unit, the Garnet-Phyllite Unit and the Phyllite Unit. These three units form concentric zon...

The Gneiss-Eclogite Unit is a composite tectonometamorphic unit within the Variscan Erzgebirge mega-antiform. It comprises migmatitic para- and orthogneisses, high-temperature (HT) mylonites, kyanite-bearing granulites, eclogites and garnet peridotites. Four different quartzo-feldspathic assemblages are recognized, in which maximum conditions of up...

Dans la Cordillère de la côte (Chili central), la série occidentale est constituée de roches détritiques d'âge paléozoïque qui ont subi des conditions métamorphiques maximales à haute pression et basse température. Cependant, elles sont rétromorphosées en faciès schistes verts. Des phengites à haute teneur en silice et des reliques d'amphiboles ble...

Single zircons from two orthogneiss complexes, the Grey Gneiss and Red Gneiss, the lowermost tectonic units in the Erzgebirge, were dated. The grey Freiberg Gneiss is of igneous origin and has a 207Pb/206Pb emplacement age of 5507 Ma. A quartz monzonite from Lauenstein contains idiomorphic zircons with a mean 207Pb/206Pb age of 5557 Ma as well as x...

The Odenwald Crystalline Complex is subdivided into four structural units (Fig. 1; Krohe 1992). These units also show strong variations in P-T histories (see Willner et al. 1991 for detailed P-T data and discussion). They can be considered as tectonic slivers of mid-crustal rocks that were juxtaposed during the Variscan orogeny along a complex syst...

The Bushmanland subprovince of the Namaqua Mobile Belt is characterised by HT/LP metamorphism around 1100 Ma over a 200-300 km-wide zone with continuous N-S zoning from amphibolite to granulite facies terranes. The thermal peak of metamorphism is preceded by convergent tectonics with thrusting of previously thinned crust and major intrusions of syn...

Tourmalinites as proximal fades equivalents of stratiform peraluminous metamorphic rocks occur stratigraphically below base metal deposits and above thick metarhyolite horizons. Their premetamorphic protoliths are believed to have originated by tourmaline precipitation from exhalative B-, F- and W-rich brines also transporting aluminous clay colloi...

Geothermobarometric studies of plutonic and medium to high grade metamorphic rocks of the Odenwald (SW Germany) provide data for the construction of PT-paths of four different crustal sections within a part of a magmatic arc of the Mid-European Hercynian orogen. The evolution of the thermal structure of the Odenwald is characterized by an early ge...

Stratiform peraluminous rocks in western Namaqualand — mainly sillimanite rocks and sillimanite-corundum rocks — are intercalated into metapelites of the Mid-Proterozoic Bushmanland Sequence. Exhalative concentrations of siliceous, B-rich, zincian, calcareous, ferruginous and phosphatic composition coprecipitated locally during deposition of the pe...

Tectonometamorphic zones were defined within the lower Paleozoic basement of the NW Argentine Andes in a transitional zone between two Andean segments of different geotectonic evolution. In the Cambrian, the Pacific edge of Gondwana changed from a passive to an active continental margin. This event began with folding of a Vendian/Eocambrian sedimen...