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Mineralization related to the post-collisional reorganization in Iberia occurs along strike-slip shear zones (Sn, Au, ± U), in extremely differentiated leucogranites and pegmatites (Sn, Nb, Ta, Be, Li), in skarns (W, ± Au, ± U), and in quartz-veins with greisen (W, Sn, ± Au, ± U). Episyenites/albitites with uraninite mineralization in strike-slip shear zones yield U–Pb ages of 304 ± 6 Ma (2σ) that are identical within error with the 40Ar/39Ar age of micas grown during fabric development (306 ± 3 Ma, 2σ), suggesting shearing and formation of episyenite/albitite and uraninite mineralization are directly related. Mineral chemistry of uraninite from episyenite and deformed muscovite-rich leucogranite host are indistinguishable and has immobile element signatures typical for uraninite that formed from a hydrothermal or metamorphic fluid. The mineral chemistry of uraninite hosted in the deformed muscovite-rich leucogranite, together with the large time span between granite emplacement (347.6 ± 1.9 Ma, U–Pb zircon) and uraninite (chemical age 300 ± 3 Ma) excludes a magmatic origin of uraninite. Mass balance indicates that leaching of rock-forming minerals (especially muscovite and monazite) of the muscovite-rich leucogranite during extensive metasomatism (e.g. albitite or episyenite formation) could provide most uraninite-hosted U. The precipitation of the uraninite-pyrite association with carbonaceous matter in episyenite/albitite was related to local reducing conditions and/or fluid unmixing processes, analogue to hydrothermal uraninite from retrograde scheelite skarn and W ± Au quartz veins in the Iberian Massif. Chemical ages of uraninite from episyenite and muscovite-rich deformed granite demonstrate that episyenitization is not a late-stage Variscan process, but a post-orogenic one. Metal mobilization is structurally controlled. Chemical dating of uraninite may provide a first-order age constraint in unravelling the post-Variscan tectonic history.

The uranium (234U/238U) and radium (228Ra/226Ra) activity ratios and 87Sr/86Sr isotopic ratio in thermal groundwater, subsurface water (groundwater) and river water from Poddebice and Uniejow were determined. The uranium and radium activity ratios and strontium isotopic ratio varied from 0.629 to 1.471, from 0.396 to 4.961 and from 0.708438 to 0.710344, respectively. The results for the thermal groundwater samples showed that the radiometric method together with mass spectrometry stable strontium isotope ratio measurements can be used for underground water transport studies. On the basis of the uranium and radium activity and the strontium isotopic ratio differences in subsurface water (groundwater) and in river water, any possible water influx between these adjacent reservoirs can be observed. The obtained results exclude any water transport from surface and subsurface water to thermal ground water reservoirs in this region of Poland.

The Hämmerlein Sn-skarn deposit of the western Erzgebirge is hosted in early Palaeozoic schists and gneisses and is closely associated with one of the most voluminous granite intrusions of the Erzgebirge, the Eibenstock granite. The main valuable ore mineral in Hämmerlein is cassiterite which is disseminated in the four types of skarn occurring in the deposit, i.e., garnet, amphibole, pyroxene, and magnetite skarn. There are two scenarios for deposit formation: (1) formation of the skarn during the regional metamorphism at 340 Ma followed by mineralization during granite emplacement at 320 Ma and (2) skarn formation and mineralization directly related to the granite intrusion. Theriak-Domino thermodynamic P-T-XCO2 modelling shows that both scenarios are possible for the formation of the skarn series, but as the Rb-Sr muscovite-based age of skarn samples is 340 Ma, the first scenario is the relevant one. The skarn mineral assemblages formed during regional metamorphism, whereas cassiterite mineralization is related to younger granite emplacement and is associated with chloritization of biotite and precipitation of fluorite. These reactions changed the fluid composition and induced cassiterite mineralization.

Basanites from theTertiary Siebengebirge area of Germany (part of the Central European Volcanic Province; CEVP) have high Mg# (40·60), moderate to high Cr (4 300 ppm) and Ni (4 200 ppm) contents and strong light rare earth element enrichment, but systematic depletion in Rb and K relative to trace elements of similar compatibility in anhydrous mantle. Rare earth element melting models can explain the petrogenesis of these basanites in terms of partial melting of a spinel peridotite source containing residual amphibole. It is inferred that amphibole, indicated by the relative K and Rb depletion and the melting model, was precipitated in the spinel peridotite lithospheric mantle beneath the Siebengebirge, by metasomatic fluids or melts from a rising mantle diapir or plume. Alkali basalts and more differentiated rocks have lower Mg# and lower abundances of Ni and Cr, and have undergone fractionation of mainly olivine, clinopyroxene, Fe^Ti oxides, amphibole and plagioclase. Most of the basanites and alkali basalts approach the Sr^Nd^Pb isotope compositions inferred for the European Asthenospheric Reservoir component. Trace element constraints (i.e. low Nb/U and Ce/Pb ratios) and the Sr^Nd^Pb isotope composition of the differentiated rocks indicate that assimilation of lower crustal material has modified the composition of the primary mantle-derived magmas. High 207 Pb/ 204 Pb ratios in the differentiated lavas point to assimilation of ancient lower crustal components having high U/Pb and Th/Pb ratios. Relatively shallow melting of inferred amphibole-bearing spinel peridotite sources may suggest an origin from the metasomatized part of the thermal boundary layer. Application of new thermobarometric equations for the basaltic magmas indicates relatively normal mantle potential temperatures (1300^14008C); thus the inferred mantle ‘baby plume’ or ‘hot finger’ is not thermally anomalous.

Dill et al. (2007) present laser ablation inductively coupled plasma mass spectrometry U-Pb data for torbernite, columbite, and limonite of the Hagendorf and Pleystein pegmatites. These pegmatites, which are intruded into a late Carboniferous granite, have been dated by Glodny (1997) to 317±3 Ma (2σ; 3-point Rb-Sr mineral isochron). Dill et al. (2007) report a torbernite age of 4.55±0.02 Ma, which is in line with earlier geochronological work in the region, showing the young redistribution of U and the formation of secondary U minerals (e.g. Carl and Dill, 1983; Wendt and Carl, 1985). Dill et al. (2007) present ages of 299.2±1.9 Ma and 302±3 Ma for ferrocolumbite from Hagendorf and Pleystein, respectively, that broadly agree with the Rb-Sr age of the Hagendorf pegmatite (Glodny, 1997). In addition, they present age data of ~345 to 380 Ma for four spot analyses on ferrocolumbite from the Pleystein pegmatite and a 549 ± 12 Ma discordia intercept age for limonite and torbernite mantling this limonite from the Hagendorf pegmatite. These ages are older than the rock hosting the dated minerals. Referring to older (Lower Ordovician) pegmatites in the Tepla-Barrandian (Glodny et al. , 1998), Dill et al. (2007) argue that the ages ~345 to ~380 Ma reflect the Devonian resetting of the U-Pb systematics of columbite from Lower Ordovician pegmatites and represent inherited domains in columbite. Apparently, Dill et al. (2007) were not aware that the Hagendorf and Pleystein pegmatites had emplaced into rocks of the Moldanubian Zone, which had an entirely different evolution than the Tepla-Barrandian from where Lower Ordovician pegmatites are known (e.g. Franke, 2000; Finger et al. , 2007). Furthermore, none of the numerous U-Pb TIMS studies on columbite from pegmatites (e.g. Romer and Wright, 1992; Romer and Smeds, 1994, 1996, 1997; Mauthner …

The distribution of ore elements between melt and restite critically influences the potential of a granitic melt to develop granite bound mineralization. Distribution of Sn between restite and melt during partial melting is largely controlled by the presence of tin sequestering phases such as biotite, muscovite, titanite and magnetite in the restite. The stability of these phases controls whether or not Sn is available for dissolution into the melt. Tin released during breakdown of one Sn-bearing phase does not necessarily accumulate in the melt. Released Sn may be retained in restite rather than partition into the melt if there is a tin sequestering phase like biotite. Modeling using the Theriak/Domino program (De Capitani & Petrakakis 2010) demonstrates that major controlling factors apart from protolith composition are whole rock (WR) water content, water activity (a(H2O)), oxygen fugacity (fO2) and melt volume and sequential melt extraction. WR water content controls the modal abundances of OH-bearing minerals and, thus, influences the position of the solidus and the volume of melt produced during dehydration melting. In terms of biotite stability, WR water content plays a subordinate role, becoming only important at very low water contents. Oxygen fugacity - ranging between Fe total = Fe2+ and the hematite-magnetite buffer - influences biotite stability, extending it towards higher temperatures at elevated fO2 values. A decrease in a(H2O), on the contrary, not only lowers biotite stability towards lower temperatures, but also shifts the solidus towards higher temperatures. Even though biotite has higher contents of Sn than muscovite, in muscovite-rich rocks a substantial proportion of bulk Sn can be hosted by muscovite. Anhydrous melting of such rocks does not necessarily lead to a Sn-rich melt, as large quantities of the released Sn may be re- distributed from the melt into restitic biotite. Biotite has a higher thermal stability than muscovite and acts as a tin sequestering phase. Therefore, temperatures of metamorphism need to exceed biotite stability to generate tin enriched melts. Those conditions are not met by internal heating alone. Additional advective heat input is needed to reach biotite stability limits. Sedimentary, tin enriched protoliths show a distinct enrichment in Al and K and depletion in feldspar bound elements (Ca, Na, Pb, Sr). Prograde metamorphism of these protoliths produces considerable amounts of muscovite. Dehydration melting of this muscovite results in the generation of large amounts of melt over a narrow temperature interval. The increase in melt volume also increases the probability of melt extraction from the migmatite. As the melt volume produced during biotite dehydration melting is relatively small and previous melt extraction(s) are very likely, tin released during biotite breakdown is distributed into a small amount of melt. These melts have elevated tin concentrations, even before further enrichment during magmatic fractionation starts.

S 5. The cycling of hydrogen, carbon, and mobile elements in the subduction factory Abstract S5-32

The Hämmerlein Sn-skarn deposit is associated with gneisses and schists which reached peak metamorphic conditions at 340 Ma. The deposit formed around 320-325 Ma, when the Eibenstock granite was emplaced, resulting on the migration of magmatic fluids along the contacts of different units. This induced decarbonation of the marble layers and the development of a series of contrasting skarns. The different units are garnet skarn, amphibole skarn, pyroxene skarn and magnetite skarn, with intercalated layers of schist and gneiss. Cassiterite is the main ore mineral. It occurs as coarse grains (up to 1mm) in the schists, as medium grains (~500 μm) at contacts between amphibole and magnetite skarn and as fine (

Primary Sn, W, and/or Ta mineralization is closely related to highly evolved granitic rocks. Not all highly evolved granitic rocks show associated mineralization, which implies that magmatic processes (e.g., fractionation, phase separation) certainly are necessary, but not sufficient. Instead, the potential of highly evolved granites to form Sn, W, and/or Ta mineralization may be primarily related to their source rocks and the melting of these source rocks. The formation of Sn, W, and/or Ta mineralization involves a sequence of processes that operate in different tectonic settings and that may be widely separated in time, i.e., (i) source enrichment, (ii) source accumulation, and (iii) metal mobilization from the source. The sequence of these processes controls the distribution of mineralization in belts (and gaps within these belts). Magmatic processes and interaction of the melts and fluids with the wall rocks at emplacement level, however, control size, grade, shape, and kind (vein, greisen, skarn) of mineralization.(i) Intense chemical alteration of silicate rocks at the surface results in the preferential loss of most feldspar-bound elements (e.g., Na, Ca, Sr, and Pb) and in the residual enrichment of elements incorporated in or adsorbed on clay minerals (e.g., Li, K, Rb, Cs, Sn, and W). Thus, exogenic processes produce some of the hallmark geochemical signatures of tin granites that are also obtained by extreme magmatic fractionation of granitic melts. Intense chemical alteration occurs in tectonically stable areas with limited topography, as for instance in the interior of large continental masses. (ii ) Source accumulation involves two separate processes, i.e., sedimentary and tectonic accumulation. Sedimentary accumulation occurs when these blankets of chemically intensely altered sediments are redistributed from the “top” of the continent to the margins of the continent during supercontinent fragmentation. Tectonic accumulation may occur when passive-margin sedimentary packages are reworked in an active margin setting. Source accumulation may be particularly important when delta deposits become tectonically stacked.(iii) The nature of heat source controls the type of melting of the crustal source rocks and the partitioning of metals between melt and restite. Sn and W are preferably bound to biotite and are distributed into the melt during biotite consumption at high melting temperature. Ta is enriched in muscovite that melts at lower temperature. High melting temperatures are only possible by heat input from the mantle by (a) mantle-derived melts in subduction settings, (b) emplacement of ultrahigh- temperature metamorphic rocks that had been subducted to mantle depth during continental collision, and (c) mantle -derived melts in extensional settings. Internal heating in orogenically thickened crust only generates minimum-temperature melts. The age of mineralization reflects the event of heat input. The superposition of source enrichment (on supercontinent), source accumulation (at continent margin), and heat input (at plate boundary) explains both (i) the distribution of Phanerozoic primary tin, tungsten, and tantalum mineralization and (ii) their irregular distribution along these belts, (iii) their contrasting age within a particular belt, (iv) their relation to contrasting tectonic settings within a single belt, and (v) their presence on both sides of major sutures.

Fault-related veins and cements from two segments [Arava Fault (AF), Ghab Fault (GF)] and one branch [Serghaya Fault (SF)] of the major transform plate boundary between Africa and the Arabian plate, the Dead Sea Transform, were investigated geochemically. The results document considerable differences in the nature and degree of fluid–rock interactions among these faults. Within the area of the AF, fluid activity has neither led to intensive exchange reactions between fluids and rocks nor to notable cementation of the fault damage zones. Strontium and carbon and oxygen isotopes indicate infiltration of predominantly descending (meteoric water) and only subordinate involvement of ascending hydrothermal fluids from deep sources. For the SF, fluid-enhanced weakening mechanisms (chemical alteration processes) and fracture cementation are dominant. Along the GF, alteration processes and fracture healing by cementation are more intense than in the AF, but less intense than in the SF branch. For the SF and GF, δ18O, strontium isotopes, and major and minor element contents of veins indicate (i) near-surface, low-temperature meteoric fluids that show little or no interaction with carbonate host rocks; and (ii) meteoric fluids that were buffered by the surrounding host rocks. We suggest that the contrasting fluid–rock interactions along the Dead Sea Transform are related to local variations in climate (precipitation).

Geological and geochemical studies have been conducted on the Arava fault segment, which forms the major branch of the Dead Sea transform between the Dead Sea and the Gulf of Aqaba. Mesoscale to microscale faulting and veining related to this fault are described from limestone sequences of two locations (areas A and B) that represent different depth sections. In area A, pressure ridges expose the exhumed fault. Deformation mechanisms indicate that faulting took place at temperatures between 150°C and 300°C, which suggests faulting depths between 2 and 5 km with respect to published geothermal gradients. In area B, brittle fault damage forms a zone up to 150 m wide. The fault core is not exposed. Faulting took place at temperatures below 200°C (up to a 3‐km depth). In both areas, we found indications for a strong fault. Our kinematic analysis exhibits that the angle Ψ between δ1 and the strike of the Dead Sea transform immediately adjacent to the fault is ≤45°. The twin‐density technique yields di...

U-Pb isotopic analyses using TIMS and Laser Ablation-Multi Collector-ICP-MS were carried out on columbite-tantalite minerals from three suites of rare-element (Li, Cs, Ta) pegmatites in the Superior Province of Canada. Conventional TIMS analyses of these columbite-tantalite crystals produce scattered data and reverse discordance even after HF leaching of the grains prior to dissolution, possibly reflecting the incomplete removal of the open-system metamict segments during sample preparation. LA-MC-ICP-MS analyses of unleached, primary columbite free from inclusions and alteration give consistent and precise (

The Saxo-Thuringian Zone includes an Autochthonous Domain that was little affected by the Variscan orogeny and an Allochthonous Domain that includes Variscan high- strain and high-grade rocks. The two domains became juxtaposed against each other during the final stages of the Variscan orogeny along the Wrench-and-Thrust Zone. All three structural elements include the same lithologies. The voluminously most important units are the Cadomian basement (a former magmatic arc) and Sn-W enriched Ordovician sedimentary rocks and their metamorphic equivalents. Late Variscan and post-Variscan magmatism in the Saxo-Thuringian Zone largely is related to the emplacement of the Allochthonous Domain (338-333 Ma), crustal melting within the Allochthonous Domain (327- 318 Ma), and repeated post-Variscan extensional reactivation of older structural elements (305-275 Ma) within the orogenic foreland (Autochthonous Domain) and to a lesser extent in the Allochthonous Domain. This magmatism occur in different tectonic settings and in part tapped different sources. Therefore, granites within the Saxo-Thuringian Zone allows to elucidate the relation between (i) source enrichment, (ii) sedimentary and tectonic accumulation of Sn-enriched soure rocks, and (iii) the heat source for the development of Sn-specific granites and possible Sn mineralization. The 338-333 Ma old intrusions include mantle-derived material or formed in contact with the ultrahigh-temperature Saxon granulites. They did not involve Sn-W enriched Ordovician sedimentary rocks. They do not show Sn-enrichment or other geochemical fingerprints distinctive for Sn-specific granites. The 327-318 Ma old granites of the Allochthonous Domain are crustal melts with I-, A-, and S-type affinity and fall in two different geochemical groups depending on source rocks. The first group has flat Upper Continental Crust (UCC)-normalized pattern, shows a weak anomaly in Sn, Cs, and Li, but has no associated mineralization. The second group has UCC-normalized pattern with distinct enrichment in Sn, W, Nb, Ta , and depletion in Sr, Ba, and Eu even in the least evolved granites. These granites typically show associated Sn mineralization. The 305-275 Ma old granites have I- and S- type affinity and show the same chemical pattern as the 327-318 Ma old granites of the Erzgebirge. Flat UCC- normalized pattern are found in granites from Thuringia and the rhyolitic volcanic and subvolcanic rocks in the foreland of the Variscan orogen. They all have slightly enhanced Sn contents, but no mineralization. Granites of the second group of the 305-275 Ma old granites resemble the 325-318 Ma old Sn-specific granites of the Erzgebirge and occur in Thuringia and the Erzgebirge, where they show associated mineralization. The contrasting chemical signature of the granites is inherited from the crustal source rocks: (i) the volcanic rocks of the Variscan foreland have an arc signature, even though they post-date subduction by more than 40 Ma. (ii) Enhanced Sn contents occur only in areas where Ordovician sedimentary rocks significantly contributed to the melts. Mineralization occurs only in areas with extensive tectonic stacking of Ordovician Sn-enriched sedimentary rocks and heat sources that allow for high-temperature melting and, therefore, is restricted to the Allochthonous Domain. Mineralization is particularly well developed in the Erzgebirge as thick packages of Sn-enriched sedimentary rocks have been extensively stacked during the Variscan orogeny and the emplacement of UHT rocks provided the heat for crustal melting.

The name coticule was first used for spessartine-bearing quartzites (Renard 1878) that represent metamorphosed finegrained Mn-rich sedimentary rocks. Based on metamorphic conditions and the composition of the siliciclastic sedimentary protolith, coticules contain different Mnminerals such as carpholite, hausmannite, or Mn-versuvianite. Although the Mn-rich sediments of the type locality were deposited on the continental shelf, the term coticule also was incorrectly applied to metamorphosed Mn-rich deep marine deposits and even exhalites. Within Variscan Europe and Acadian North America, coticules sensu Renard (1878) occur in sedimentary units deposited on the continental shelf and typically are of Ordovician age (Romer et al. 2011). Most importantly, they seem to be restricted to the Avalonian shelf. The provenance of the metasedimentary rocks of the Monotonous (Ostrong) and Variegated (Drosendorf) units of the Moldanubian Zone is not well constrained. There are however rare occurences of Mn-rich sedimentary rocks. We investigate whether these rocks show the geochemical and isotopic features of coticules from the Avalonian shelf, e.g., those from Nova Scotia (Canada) and the Ardennes (Belgium), which would provide a provenance proxi, and whether they also have an early Palaeozoic age. CONSTRAINTS FOR COTICULE FORMATION Mn-rich sediments form when redoxcontrolled dissolution and precipitation of Mn (and Fe) keeps pace with siliciclastic input, i.e., in sediment-starved settings. Early Palaeozoic coticules on Avalonia formed when sediment input from Avalonia was drastically reduced and the subordinate sediment component derived from Gondwana became chemically and isotopically distinct in the coticule-bearing layers, most prominently by negative Ndtvalues, elevated 87Sr/86Sr, and the REEpattern.

The Saxo-Thuringian Zone is pivotal for understanding the Variscan evolution of Central Europe, as this part of Gondwana was one of the first to collide with Laurussia. The Saxo-Thuringian Zone comprises domains that have experienced variable degrees of Variscan metamorphism ranging from medium grade to UHT/UHP in some domains, while other parts were largely unaffected by deformation or metamorphism. These differences in overprint reflect pre-Variscan crustal heterogeneity and thickness variation, where thinner segments were wedged into the subduction zone and rigid, thicker blocks escaped subduction. The heterogeneity of crustal thickness is considered to be caused by Ordovician rifting (470-480 Ma) of the Cadomian crust (570-540 Ma) at the Gondwana margin. Today, magmatic and sedimentary rocks deposited on the thin crust of these rifts form the metamorphic complexes of the Saxon Granulite Massif and the Erzgebirge Mtns. Variable response of crust of different thickness to Variscan deformation and metamorphism is not particular to the Saxo-Thuringian Zone, but rather a typical feature of the crust all over Variscan Europe. The 18 chapters of this book are review and synthesis papers and present overviews of the Cadomian evolution, the post-Cadomian development of the passive margin, a state of the art assessment of the biostratigraphic record of Saxo-Thuringian sediments, various aspects (metamorphism, structure, magmatism) of the Variscan reworking of the Saxo-Thuringian Zone and processes related to the erosion of the Variscan Orogen. Extensive references include also older, generally difficult to find literature references, PhD theses and original descriptions published in very local journals. This book makes use of, and in part provides, previously unavailable maps and borehole data, largely acquired in GDR time in the course of exploration for uranium, fossil fuels, and ore minerals. The geological sheet map of the Pre-Permian geology of Eastern Germany, based on this material and compiled by SDAG Wismut (now WISMUT GmbH), is included and made available for the first time to a wider audience. Numerous figures and additional materials are provided on the enclosed DVD.

The geochemistry and mineralogy of lamproites from southwestern Anatolia can be used as a snapshot of the lithospheric composition beneath the Menderes Massif. High and near-constant K2O contents, the presence of mantle xenocrystic phlogopite and olivine, highly magnesian olivine phenocrysts and Cr-rich spinel inclusions all indicate that the lithospheric mantle was phlogopite-bearing ultradepleted harzburgite at the time of lamproite eruption (20-4 Ma). This mantle assemblage most probably originated in a complex multistage process, including (intra-oceanic) supra-subduction zone depletion during the final stages of southern Neotethyan ocean closure, and accretion of the forearc oceanic lithosphere as shallowly subducted material to the already assembled Anatolia. The data presented here support shallow subduction of the oceanic lithosphere as a cause of the uplift of the Menderes Massif, in contrast to the traditional core-complex model.

Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (similar to 20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the mu m to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.