This paper presents an updated synthesis of morphotectonic studies that quantify active tectonics along the Gurvan Bogd mountain range in the Mongolian Gobi-Altay, the site of one of the strongest historic intracontinental earthquakes (Mw 8.1) in 1957. Our goal was to determine the slip rate along the constituent fault segments and to estimate the return period of such large events. Along each segment, cumulative offsets were estimated from topographic surveys, and the ages of the offset markers were determined using cosmic-ray exposure dating. In this review, we reevaluate 10 Be data reported in previous publications using a chi-square inversion analysis of depth profiles and an updated scaling model for spatial production rate variations. We also discuss sampling strategies for dating alluvial fans in arid settings. This study confirms the low horizontal and vertical slip rates within the massifs of the Gurvan Bogd mountain range for the Late Pleistocene–Holocene period, suggests that episodes of aggradation occurred near the times of major glacial-interglacial terminations (at ca. 15–20 ka and ca. 100–130 ka), and provides evidence for another much earlier aggradational episode, occurring before 400 ka. The Bogd fault has a maximum horizontal left-lateral slip rate of ∼1.5 mm/yr, while reverse fault segments along the Gurvan Bogd fault system have vertical slip rates between 0.1 and 0.2 mm/yr. Characteristic dislocations observed along the Bogd fault suggest return periods of earthquakes similar to 1957 between 3000 and 4000 yr.

Abstract The Elatsite porphyry copper deposit is situated 6 km south of the town of Etropole, in the northern part of the Panaguyrishte-Etropole ore region (Figs. 1 , 2 ) as part of the Elatsite-Chelopech ore field (Appendix 2, 5). The deposit is located about 10 km NW of the Chelopech volcanic center. It is emplaced along the contacts of Upper Cretaceous dykes (porphyry granodiorite, quartz dioritic or monzo-syenodiorite) with the Precambrian-Cambrian phyllites (Figs. 2 , 3 ; Appendix 5). The phyllites are contact- metamorphosed to hornfels adjacent to the dykes and Paleozoic granodiorite. The dykes dip to the south toward the magma chamber of the volcano-intrusive structure (Fig. 4 ). Porphyry Cu-Au-PGE mineralisation (Re/Os age 92–92.4 Ma; Zimmerman et al., 2003 ) is genetically connected to Late Cretaceous subvolcanic intrusions of quartz-monzonitic to granodioritic composition (U/Pb age 91.5–92 Ma; von Quadt et al., 2002 ), but it is also hosted in Paleozoic granodiorites (314 Ma; von Quadt et al., 2002 ) and in greenschists. The porphyry ore stock has a lens-like shape elongated to the NE, and it dips at 40°–50° to the South; it is 1,300 m long and 200 to 700 m wide. At depth the ore- body was traced more than 550 m. The porphyry- copper, Mo, Au and PGE mineralisation is hosted mainly in the granodiorites, but it is also abundant in porphyry dykes of quartz syenodiorite (Figs. 5 , 6 ) and is best developed

Abstract The Panagyurishte ore district is located in a 30 × 50 km belt trending N-NW and S-SE of the town of Panagyurishte in the central Srednogorie, Bulgaria (Fig. 1 ; Appendix 1, 3). The region was named by Bogdanov (1981) as the “Panaguyrishte-Etropole ore district,” which includes the porphyry copper deposit Elatsite and the ore-bearing territory around the town of Etropole (Fig. 1 ). The district belongs to the Late Cretaceous Banat-Srednogorie metallogenic zone, part of the European Alpine belt ( De Boorder et al., 1998 ; Neubauer et al., 2002 ). The zone, also known as the Banatititic magmatic and metallogenetic belt (BMMB) ( Berza et al., 1998 , Ciobanu et al., 2002 ; Heinrich and Neubauer, 2002 ) was formed as a result of Late Cretaceous subduction-related magmatic activity. The Srednogorie part of the metallogenic zone in Bulgaria developed during the Mesozoic as a copperrich, andesite-dominated island arc system (Fig. 1 ) that continues eastwards through Turkey to Iran. ( Jankovic, 1977 , 1997; Bogdanov, 1987 ; Dabovski et al., 1991 ; Heinrich and Neubauer, 2002 ). A series of epithermal volcanic rock-hosted ore deposits (e.g. Radka, Elshitsa and Krassen) related to Late Cretaceous andesite-dacite volcanic activity are located in the southern part of the Panagyurishte ore district (Figs. 1 , 2 ), close to small porphyry copper ore deposits (Vlaikov Vruh, Tsar Assen, Petelovo) hosted by co-magmatic subvolcanic monzodiorite, granodiorite and quartzdiorite porphyry intrusions. Two main

In this century, western Mongolia and the area adjacent to it in China have been one of the most seismic intracontinental regions of the world. Four earthquakes with magnitudes (M) ≥ 8 have occurred. Average displacements of several meters along ruptures more than 100 km long characterize all of them. The dominant style of faulting for each was strike-slip: left-lateral on easterly trending planes in the 1905 Bulnay and Tsetserleg earthquakes and in the 1957 Gobi Altay earthquake and right-lateral on a north-northwesterly trending Fu-yun fault in 1931. The ruptures associated with these earthquakes, with most other, smaller earthquakes, and with one older great earthquake suggest that western Mongolia is undergoing conjugate strike-slip deformation. Equivalently, the region undergoes northeast-southwest shortening and northwest-southeast extension. The component of shortening can be seen as a manifestation of the convergence between India and Siberia. The component of extension seems to mark a transition from an area of largely crustal shortening in China to another, the Baikal Rift system, where crustal extension is dominant. The average rate of seismic deformation in western Mongolia in this century consists of 49 (± 15) mm/a of northeast-southwest shortening and 40 (± 12) mm/a of northwest-southeast extension. Such high rates imply strongly that the twentieth-century seismicity has been abnormally high. Moreover, crude estimates of average recurrence intervals for great earthquakes on the Bulnay fault and in the Gobi Altay region are about 1,000 yr. Approximate Holocene or late Quaternary average slip rates on these faults are a few millimeters per year, suggesting that Mongolia is being sheared left-laterally with respect to Siberia at about 10 mm/a (between 5 and 20 mm/a). A similarly crude estimate for right-lateral slip along the northwest-trending Mongolian Altay is also 10 mm/a. We suspect that this right-lateral shear is a manifestation of the left-lateral regional shear parallel to east-west planes and of counterclockwise rotation of both the Mongolian Altay and the strike-slip faults within the range. Correspondingly, the eastward translation of western Mongolia with respect to Siberia manifests itself as crustal extension and rifting along the Hövsgöl and Baikal rift zones. In the Hangay, the broad upland in the interior of western Mongolia, scattered minor normal faulting with no obvious preferred orientation appears to be the common style of deformation. This area seems to be underlain by the same relatively hot upper mantle that underlies the Baikal rift system. Thus, as others have suggested, the collision between India and Eurasia does not appear to be the only cause of the active tectonics of western Mongolia. The perturbations to the stress field in the crust resulting from the emplacement (and upwelling) of hot material beneath the Baikal area and the Hangay and Hövsgöl uplands also play a key role in the active tectonics. Finally, the active deformation in western Mongolia appears to be young. Some surface faulting bears no obvious relation to the present topography. The very flat summit of Ih Bogd, the highest peak in the Gobi Altay, may have risen from the surrounding lowlands since only 1 Ma. Thus, the rapid deformation in western Mongolia seems to have begun tens of millions of years after India collided with Eurasia, perhaps as recently as a few million years ago.

Abstract A chain of plutons (Plana, Gutsal, Varshilo, Lesichovo, and Elshitsa-Boshulia) of granite to granodiorite composition is situated in the southern part of central Sredna Gora zone at the border with the Rhodope massif (Fig. 1 ). Relatively large lenses and sheet-like bodies of mafic rocks (gabbros, gabbro-diorites, and diorites) are imbedded in the granitoid host. Numerous mafic fragments in the granites often accompanied these mafic bodies (Fig. 1 ). Previous investigators considered these intrusive bodies as products of magmatic activity during two magmatic epochs: Veriscan time for the Varshilo and Lesichovo plutons and Late Cretaceous (or Late cretaceous-early Tertiary) time for the Plana, Gutsal, Elshitsa, and Boshulia plutons (Fig. 1 ). The latter have been interpreted as a “fracture intrusions” formed in a rift setting ( Dabovski, 1968 ) and as products of multiphase or double-phase normal basaltic magma differentiation ( Dimitrov, 1933 ; Boyadjiev, 1979 ). The mafic varieties are supposed to be older than the granites. The mafic fragments have been considered as xenoliths from the country rocks. Based on petrostructural magnetic (accelerator mass spectrometry) studies, our interpretation emphasises two key points: the crustal-scale dextral strike-slip Iskar-Yavoritsa shear zone controlled the intrusions; and granitic and gabbroic magmas were generated at different levels in the crust and were mixed (s. l.). The Iskar-Yavoritsa shear zone is a NW-SE regional dextral strike-slip fault that can be traced south-southwestward of Sofia at a distance 80–90 km (Fig. 1 ).

Abstract The Panagyurishte ore region is located 55-95 km east of the city of Sofia. It covers an area of about 1,500 km 2 that includes part of the central Srednogorie and Stara Planina Mountains between the towns of Pazardjik and Etropole. The region is named after Panagyurishte—a town located in the center of the area. Geology of the region is determined by an area of intense Late Cretaceous magmatic activity related to its ore deposits. More than 150 ore deposits and ore occurrences and mineral indications are found in the region, which is characterized mainly by porphyry copper and epithermal massive Cu-Au deposits as well as small gold, gold and base-metal, barite, lead-zinc, and manganese deposits and ore occurrences (Appendix 1). Alluvial gold placers are also established here. Copper- and gold-bearing ores have been mined from ancient times. Contemporary geological studies and active mining were begun in 1936 by the French business, Company Orient, later renamed Luda Jana. During the period 1940-1942, the deposits became a state property. After intensive geological studies during the decades after World War II, several mines in the region were opened—the porphyry copper deposits, Medet, Vlaykov Vruh, Assarel, Tsar Assen, and Elatsite; the massive sulfide copper-pyritic deposits of Krassen, Elshitsa, Radka; the massive-sulfide coppergold deposit at Chelopech; the vein gold deposit at Negarshtiza; the gold and base-metal deposit at Dolna Kameniza; and the barite mine at Kashana (Appendix 1). From 1942 to 1995 the region produced 489,400 t ore: 3,946,092 t copper (in ore), 665,185 t

Abstract The Palaeoproterozoic crust and upper mantle in the region between the Ukrainian and Baltic shields of the East European Craton were built up finally during collision of the previously independent Fennoscandian and Sarmatian crustal segments at c . 1.8–1.7 Ga. EUROBRIDGE seismic profiling and geophysical modelling across the southwestern part of the Craton suggest that the Central Belarus Suture Zone is the junction between the two colliding segments. This junction is marked by strong deformation of the crust and the presence of a metamorphic core complex. At 1.80–1.74 Ga, major late to post-collisional extension and magmatism affected the part of Sarmatia adjoining the Central Belarus Zone and generated a high-velocity layer at the base of the crust. Other sutures separating terranes of different ages are found within Sarmatia and in the Polish–Lithuanian part of Fennoscandia. While Fennoscandia and Sarmatia were still a long distance apart, orogeny was dominantly accretionary. The accreted Palaeoproterozoic terranes in the Baltic–Belarus region of Fennoscandia are all younger than 2.0 Ga (2.0–1.9, 1.90–1.85 and 1.84–1.82 Ga), whereas those in Sarmatia have ages of c . 2.2–2.1 and 2.0–1.95 Ga. Lithospheric deformation and magmatism at c . 1.50–1.45 Ga, and Devonian rifting, are also defined by the EUROBRIDGE seismic and gravity models.

Abstract The Carpathian-Balkan (Apuseni-Banat- Timok-Srednogorie belt) Late Cretaceous metallogenic and magmatic province is particularly well suited for the study of genetic relationships between calc-alkaline magmatism and porphyry-style and epithermal ore deposits. Here, igneous and hydrothermal products are still linked to the present-day lithosphere structure as depicted by seismic tomography ( Sparkman, 1986 ; Wortel and Sparkman, 2000 ). The products of magmatism in the province reveal the interaction of processes from the lithospheric scale down to individual ore-magmatic centers. This magmatism also gave rise to fertile ore-forming magmatic-hydrothermal systems of great practical significance ( Mitchell, 1996 ; Jankovich, 1997 ). Europe's only world-class porphyry- copper deposit (Medet) and Europe's largest gold producing mine (Chelopech; Andrew, 1997) are related to this magmatism. In spite of many publications describing the geology, tectonics, and ore mineralization of the Srednogorie part of the province, up-to-date regional summaries of its petrology and geochemistry are lacking. Most past ideas were based on unreliable geochemical data. The relative and absolute timing of this magmatism within the geodynamic evolution of the region was predicted but not well supported. The geochronological constraints published before 2000 were based mainly on K-Ar methods ( Chipchakova and Lilov, 1976 ; Boyadjiev, 1981; Boyadjiev and Lilov, 1981; Lilov and Chipchakova, 1999 ). On the other hand, abundant new data for central Srednogorie that has accumulated during recent years, although valuable, were concentrated on specific ore-magmatic centres ( Amov, 1999 ; Kouzmanov et al., 2001b ; Velichkova et al., 2001