ALBERT

Description: New stratigraphic, major- and trace-element, and Sr-, Nd- and Pb- isotopic data on volcanic deposits older than 14 ka from the island of Procida, Italy, are presented and compared with published analyses from the rest of the Phlegraean Volcanic District (PVD). Procida rocks range in composition from basalt to shoshonite and trachyte and show 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios varying within the ranges 0.70523–0.70678, 0.512539–0.512630, 18.99–19.29, 15.67–15.69 and 39.10–39.39, respectively. The presence of a compositional gap in the range SiO2=54–59 wt % is evidence of magma bimodality, and suggests that the feeding magmatic system was formed by at least two different reservoirs located at different depths. Geochemical and isotopic variations with increasing differentiation can be explained by fractional crystallization mechanisms, that in some cases were associated with crustal contamination that occurred in both deeper and shallower reservoirs; the most evolved magmas formed in the shallower one. Mixing/mingling processes also occurred. The variation of isotopic composition through time observed both for Procida and for Campi Flegrei and Ischia rocks is evidence of strong affinity between magmas that erupted on the entire PVD until about 40 ka. This indicates that they share a common origin and a common plumbing system. Most of the PVD eruptive centers active until about 40 ka lie within a NE-SWoriented volcano-tectonic belt extending from the southeastern part of Ischia, through Procida and Torregaveta volcano to the northeastern sector of the present Campi Flegrei caldera. This not only indicates the existence of a link between regional structures and volcanism in the area, but also suggests that PVD magma genesis and evolution were strongly regulated by extensional tectontectonics. In the last 40 ka the mafic rocks erupted along this extensional structure – from Torregaveta and the islands of Ischia and Procida – indicate that it still represents an important crustal discontinuity that focuses mantle-derived magmas. Procida trachybasalts are enriched in large ion lithophile elements (LILE) and light and middle rare earth elements (LREE and MREE), and show slight negative anomalies in the high field strength elements (HFSE) relative to average MORB. A slight depletion in HREE is present. Trace element and isotope systematics can be referred to a lithospheric mantle source. The lithospheric mantle source carries intra-plate and slabderived components, the latter probably inherited from a previous subduction event.

Description: Published

Description: 622-641

Description: partially_open

Description: This study summarizes the results of structural, geochemical and seismological surveys carried out at Nisyros volcano (Aegean Sea, Greece) during 1999–2001. Field mapping and mesostructural measurements at the summit caldera (Lakki plain) indicate that faults follow two main strikes: NE-SW and N-S. The N-S striking fault depicts extensional features accommodating the left-lateral component of motion of the NE-SW- striking main faults. The NE-SW preferred strike of the Lakki faults and of the mineral-filled veins as well as the distribution and NE-SW elongation of the hydrothermal craters indicate that tectonics plays a major role in controlling the fluid pathway in the Nisyros caldera. The same NE-SW trend is depicted by CO2 anomalies revealed through detailed soil CO2 flux surveys, thus indicating a structural control on the pattern of the hydrothermal degassing. Degassing processes account for a thermal energy release of about 43 MW, most of which occurs at Lofos dome, an area that was affected by hydrothermal eruptions in historical times. The seismic study was conducted in June 2001, using a deployment specifically aimed at detecting signals of magmatic-hydrothermal origin. Our instruments recorded local and regional earthquakes, a few local longperiod events (LP), and bursts of monochromatic tremor. Local earthquake activity is concentrated beneath the caldera, at depths generally shallower than 6 km. Planewave decomposition of tremor signal indicates a shallow (〈200 m) source located in the eastern part of the caldera. Conversely, LP events depict a source located beneath the central part of the caldera, in the area of Lofos dome, at depths in the 1–2-km range. In agreement with geochemical and structural measurements, these data suggest that both the deeper and shallower part of the hydrothermal system are subjected to instability in the fluid flow regimes, probably consequent to transient pressurization of the reservoir. These instabilities may be related to input of hot fluids from the deeper magmatic system, as suggested by the variations in geochemical parameters observed after the 1997–1999 unrest episode. The significance of seismological and geochemical indicators as precursors of hydrothermal explosive activity at Nisyros is discussed.

Description: Published

Description: 358-369

Description: partially_open

Description: 1. Tectonics and structure of the Pamirs - S. V. Ruzhentsev and V.A. Shvolman 2. Metamorphic events in Ladakh, Indus suture zone Karakorum - M. E. Brookfield 3. Peninsular and Himalayan Precambrian belts - D. P. Dhoundial 4. Structural records of orogeny and Himayalan mountainrange - Josef Jaros 5. Central Indian ridge and Himalayan mountain system - J. G. Negi. P. K. Agrawal and N. K. Thakur 6. Magmatism and crustal growth in the Himalaya - Kewal K. Sharma 7. Different kinds of thrusting in the Himalaya - G. Fuchs 8. Tectonic significance of the Himalayan active faults - Takashi Nakata 9. Himalayan and Sveconorwegian tectonics - A. Berthelsen 10. The Himalayan and Alpine anatomy - Biq Chingchang 11. Summary of Himalaya and Alpine structure - P. S. Saklani 12. The Himalayan arc system and gravity tectonics - M. N. Saxena 13. Basement listric faults and the Himalayan evolution - A. K. Dubey and M. I. Bhat 14. Palaeomagnetic data from Indo-Pakistan and South Central Asia: collision tectonics - Chris T. Klootwijk 15. Seismotectonics of Pakistan and the Central Himalaya - L. Seeber, R. Quittmeyer and J. Armbruster 16. Seismotectonics of the Himalaya - R. K. Verma 17. The Himalaya and the Indian-Asian plate interactions - S. K. Acharyya 18. Tectonic framework of ophiolite belts - S. V. Srikantia 19. Tectonic significance of magmatism in Kashmir and Kumaun Himalaya - V. Divakara Rao 20. Facies pattern of Kashmir Himalaya - S. K. Shah 21. Nappe tectonics in the Simla-Kumaun-Garhwal Himalaya - A. D. Gibbs 22. Inner schistose series of Garhwal and Kumaun - I. C. Pande 23. The Nepal Himalayan geology - C. K. Sharma 24. Stratigraphy and structure of west Nepal Himalaya - J. M. Remy 25. Tibetan slab of central Nepal Himalaya - P. Bordet 26. The K/Ar age determinations in Eastern Nepal - D. Krumenacher, F. A. Kingery - A. M. Basett and H. F. Layne 27. Inverted metamorphic sequences of the eastern Himalayan Crystallines - S. Sinha Roy 28. The Assam-Arakan orogen: basinal configuration and sedimentation - P. K. Dasgupta, R. Mukherjee and Ananya Biswas

Description: The volume consists of modern researches on the Himalayan Mountain Geology by eminent and active geoscientists of India and abroad. The formation of the Himalaya is a result of collision tectonics and the rock- material from the deep interior was exhumed for about 40 km and was horizontally transported for about 200 km along the Main Central Thrust. Historically the development of Himalayan geology was adversely affected due to World War I and II but notable contributions were made when India became independent. Two layers of Siwalik sediments underlie the alluvium: the upper Siwalik-1000m and lower Siwalik-4000m. Geophysically, it was determined that some of the faults of the Himalaya are deep rooted (12 km). Palaeogene rocks are regressive and were derived from the Indus Suture Zone. Granitoids of Kinnaur show mineralogical variations. Alkali-silica reaction in rocks plays a significant role in the rock-strength property. Rocks of the Yamuma valley were subjected to ductile and brittle-ductile deformation. Dynamic rejuvenation due to vertical uplift is observed in geomorphological features. The composite Main Central Thrust consisting of MCT-I, II and III occurs in the form of a major Duplex characterized by shortening (60%) and ramping (8 km). The rocks of the Almora Nappe were affected by pre-syn- and post-shear zones. The Mussoorie syncline consists of pop-up klippen. Imbricated slices are associated with the thrusts. The Himalayan rocks were metamorpho-sed in two distinct phases, which were progressive and retrogressive and were related with three phases of deformation. Many geomorphological features in the Himalayan region are marked by neotectonics. Geokinematics and structural patterns of the whole Himalayan/Alpine belt indicate that their structural architecture was made by compressional, rotational and strike slip movements. It is hoped that the volume would be useful to researchers, academicians and geoscientists in governmental and nongovernmental organisations of the country and abroad. 1. The Formation of the Himalaya - Maurice Brunei, Stephane Dominguez, Georges Mascle 2. Himalayan Geology: A Historical Perspective - Rasoul B. Sorkhabi 3. Magnetotelluric Studies in Northwestern Himalaya - Gautam Gupta, S.G. Gokarn, C.K. Rao and C. Selvraj 4. Sedimentology of the Palaeogene Succession in Jammu Region, Jammu and Kashmir State, NW Himalaya - B.P. Singh, D.S. Andotra and J.S. Pawar 5. Biotite from Neoproterozoic Granite Gneiss Cambro- Ordovician Granitoid and Neogene Leucogranite of Kinnaur District, Himachal Pradesh - Santosh Kumar and Brijesh Singh 6. Relation Between Mineralogical and Physical Properties of Coarse and fine Aggregates and Influence of Textural, Chemical and Dimensional Difference on Strength of Mortar and Concrete, Manali (H.P.) - S.C. Bhatt and Rajiv Kumar 7. Structure and Tectonics of the Yamuna Mylonite Zone, District. Uttarkashi, Uttaranchal - A.K. Biyani 8. Geological and Morphotectonic Studies Using Satellite Images of a Part of Tehri-Uttarkashi District, Lesser Garhwal Himalaya - A.C. Pandey, P.S. Saklani and C.S. Dubey 9. Tectonic Geology of the Main Central Thrust, Garhwal, Uttranchal - P.S. Saklani 10. Tectonic Evolution of The Almora Nappe Along the Chhara- Someshwar Transect, Kumaun Himalaya - Mallickarjun Joshi and A.N. Tiwari 11. Pop-up Klippen in the Mussoorie Syncline, Lesser Himalaya, Evidence from Field and Model Deformation Studies - A.K. Dubey and R. Jayangondaperumal 12. Development of the Thrusts in Garhwal Himalaya - Arun K. Shandilya 13. Metamorphic and Deformation History of the Central Crystallines of the Upper Alaknanda Valley, Garhwal Himalaya and its bearing on inverted Metamorphism - Surya Pratap Singh, Prem Swarup Saklani, Alan Bruce Thompson 14. Structural and Metamorphic Studies of Rocks associated with the Chail Unit and Main Central Thrust Zone of the Garhwal Himalaya - V.K. Singh 15. A Contribution to Metamorphic History of an Area of Chamoli Garhwal - B.C. Joshi 16. Neotectonic and Morphotectonic Evolution of a Part of North Eastern Kumaun Himalaya - Rameshwar Ball 17. Seismotectonic Studies in Manipur and Adjoining Areas - Arun Kumar and Manichandra Sanoujam 18. Strike-Slip Related Structural Patterns and orogenic Geokinematics of the Mediterranean-Central Asian Orogenic Belt - M. Kopp.)

Description: Contents: Foreword 1. Two orogenic systems in the Himalaya: Evidence and consequences - Jean-Pierre Burg 2. Evolution of the Kargil Basin, Ladakh Himalaya: Biostratigraphic, Palaeoecologic and Palaeoclimatic Constraints - N.S. Mathur and K.P. Juyal 3. Tectonomagmatic Evolutionary Model of the Kulu-Rampur Window, Himachal Pradesh, NW Lesser Himalaya: A Geochemical Approach - Shaik A. Rashid and Kewal K. Sharma 4. Tectonic and Geochemical Significance of Black Shale Formations in Kulu Valley, Himachal Himalaya - Rajinder Kumar, V.K. Singh and G.K. Dinkar 5. Lineament Control and Seismo-tectonic Activity of the Area Around Dharamsala, Himalayan Frontal Zone, H.P. - Sunil Dhar, S.S. Randhawa, R.K. Sood and Naval Kishore 6. Microgranular Enclaves Hosted in Champawat Granitoids, Kumaun Lesser Himalaya: Evidences of Magma Mixing, Mingling and Undercooling Processes - Santosh Kumar and B.N. Singh 7. The Natural Hazards in Uttarkashi and Tehri Districts, Uttaranchal Himalaya - D.S. Bagri 8. Morphotectonic Study of Seismic Source Area in Chamoli Garhwal - B. C. Joshi 9. Geology of the Garhwal Himalaya: Retrospect and Prospect - P. S. Saklani 10. Geology and Structure of Srinagar, Garhwal-Himalaya - Shashank Shekhar, P.S. Saklani and A.M. Bhola 11. Structural History of the Metamorphics of Almora Nappe around Champawat-Lohaghat Region, Kumaun Lesser Himalaya - Mallickarjun Joshi, A.N. Tiwari and D.C. Mamgai 12. The reconstruction of Ice Age Glaciation of the Himalaya and High Asia by Quaternary Geological and Glaciogeomorphological Methods - Matthias Kuhle 13. Electromagnetic Imaging of the Himalaya: Magnetotelluric Perspective - Gautam Gupta and S.G. Gokarn 14. Geology of the East, West and Upper Siang Districts, Arunachal Pradesh - A Synthesis - Surendra Singh 15. Stratigraphy and Sedimentation of the Upper Member of "Muth Quartzite" from Spiti and Kuti Regions, Central Himalayas, India - Pradip Kumar Das Gupta 16. Analysis of Drianage Systems of Manipur and Implications on the Tectonic Evolution of Indo-Myanmar Ranges - Soibam Ibotombi and M. Pradip Chandra Singh 17. Trace Element contamination in Loktak Lake, Manipur - Oinam Geeta Devi, R.A.S. Kushwaha and M. Okendro 18. Geological Aspects of the Eastern Himalayan Syntaxis: New Constraints from Structural, Petrologic and Zircon SHRIMP Data - Yan Liu, Hans-Joachim Massonne, Wolfgang Siebel, Xuchang Xiao 19. Analysis of Morphometric Parameters for Mass Wasting Study, Garhwal Himalaya - Kishor Kumar

Description: The volume is mainly focussed on structural and metamorphic characteristics of the Himalayan rocks exposed in various sectors of the Himalaya. The peridotites in the Spongtang nappe of Ladakh are mylonitised and occur in superposed imbrications. The regionally metamorphosed pelitic rocks of a part of Kashmir show low pressure, intermediate and medium pressure of metamorphism. The Buniyar granite is an intrusive pluton in the Dogra Slates (Precambrian) in the Western part of Kashmir. The NE-SW compressional stress was responsible for development of multiple folds in metamorphics of Chamba area. The radiometric date of granites in Chor mountain is Pre-Tertiary (1000 m.y and 525 m.y.). The metamorphic and folding processes of the Chor pelites were terminated by the Jutogh thrusting phenomena. The crystallines of Palampur (Himachal) are characterised by the Chail thrust and contain about 12 types of garnet texturally. The Manali-Rohtang Pass area forms a! part of an overturned limb of the Crystalline nappe. The thrusts in the Kumaun region developed from the hinterland to foreland. The total displacement of the Munsiari, Krol and Berinag Sheets was about 330 km. The Purola area in Garhwal is located between the Main Central Thrust and the Tons Thrust. Metamorphics in the Bhagirathi valley were formed at the temperatures ranging from 479? to 666? C. The uranium mineralisation in the granite-gneisses and the footwall quartzite took place after the formation of the Main Central Thrust III in Tehri Garhwal. The rock-fabric (b-c girdles of quartz) in rocks of Lansdowne Crystalline nappe developed along the thrust-transport direction with rotation which is exhibited by triclinic symmetry The fracture and lineament patterns were formed in the frontal parts of the Himalaya. The Lesser Himalaya region in Himachal Pradesh has overlapping crystalline thrust. The Chail nappes are traceable throughout the length of the Lesser Himalaya. The nappe thrusting in two phases occurred in Eastern Nepal during middle Tertiary and Quaternary times. Simple shear type of deformation affected the rocks in Eastern Nepal. The high heat flow in rocks of Darjiling region was responsible for the first phase of metamorphism which was followed by overturning and thrusting during the second phase of deformation. The metapelites in Eastern Sikkim are characterised by Kyanite-sillimanite isograd with associated quartzofeldspathic melt during pre-and syn-kinematic deformation. The reflected Aravalli trends are present in Arun transanticline and Tista Dome in Bhutan. The Central Tibetan region was possibly the homeland for the nappes in the Eastern Himalaya. This book would be useful to earth scientists, academicians & research scholars. 1. The Central Himalayan Gneisses in Northern Pakistan - R. D. Broughton and B. F. Windley 2. Ductile Shearing in Peridotites of Spongtang Nappe, Ladakh - I. Reuber, P. Nehlig and G. Reibel 3. Low-Pressure Metamorphism in a Regionally Metamorphic Terrain of Doda - Kashmir Himalaya, B. K. Das 4. The Buniyar Granite of the Kashmir Himalaya - T. R. Sharma and K. R. Sharma 5. The Aureole Zone and Metasediments of Dhauladhar, Chaori Khas (H.P.) - R. S. Bedi and A. K. Prasad 6. Geochronology of Bandal Granitoids, Kulu, Himachal Pradesh - N. Kishore, V. P. Singh, A. K. Kansal, A. Kumar, N. K. Sharma and Bimal Rai 7. The Jutoghs and their Structural History, Chur Area - R. C. Kanwar and I. Singh 8. Garnets from Metapelites of the Palampur Area (H.P.) - N. Chaudhri and L. N. Gupta 9. Metamorphics of Manali-Rohtang Area, NW Himalaya - S. Kumar 10. Structural Analysis of Chamba Region, Himachal Pradesh - B. K. Sharma and A. M. Bhola 11. Structures of Purola Area, Garhwal Himalaya - A. K. Pachauri 12. Mylonites of Dunda Area, Uttarakashi, Uttaranchal - R. K. Prasad 13. Metamorphics of the Bhagirathi Valley, Garhwal Himalaya - P. S. Saklani and V. K. Bahuguna 14. Uranium Mineralisation around Raunsal, Uttaranchal - G. R. Narayan Das, G. S. Bhatnagar, A. K. Bhattacharya and Y. C. Sharma 15. Naini-Group/Nappe Rudraprayag (Garhwal Himalaya) - S. Varadarajan and R. S. Rawat 16. Fabric of the Amri Tectonites, Lansdowne Area, Uttaranchal - S. N. Sarkar and S. M. Dutta 17. Tectonics of Central Crystallines Nappes, Garhwal Himalaya - P. S. Saklani 18. Reinterpretation of the Tectonics of the Central and Southern Lesser Himalaya, Uttaranchal - V. K. Gairola 19. Structural Evolution of the Kumaun Lesser Himalaya - M. R. W. Johnson 20. Structure of the Kumaun Lesser Himalaya - K. S. Valdiya 21. Central Crystallines and Main Central Thrust, Eastern Kumaun Himalaya - V. C. Thakur and B. K. Choudhury 22. The North Almora Thrust Zone, Kumaun Himalaya - D. B. Yedekar and K. B. Powar 23. Fractures and Lineaments in the Lesser Himalaya of Kumaun - R.N. Pande, G. Dikshit and D. N. Kanungo 24. The Chail Nappes in the Himalaya - G. Fuchs 25. Chail Metamorphics of the Himachal Pradesh - N. S. Virdi 26. Relief Thrusts in the Eastern Nepal Himalaya - J. Jaros and J. Kalvoda 27. Structure and Metamorphism in Eastern Nepal - Y. Maruo and K. Kizaki 28. Mesoscopic Structures and Tectonics of the Central Nepal Himalaya - W. Bogacz and J. Krokowski 29. Harrovian Metamorphism of Takdah, Darjeeling (Eastern Himalaya) - R. K. Lal, S. Mukherji and D. Ackermand 30. Deformation and Strain of the Himalayan Nappes: Sikkim, Eastern Himalaya - S. Sinha Roy 31. The Bhutan Himalaya: Stratigraphy and Structure - B. S. Jangpangi 32. Eastern Himalayan Stratigraphy and Tectonics - S. K. Acharyya 33. Structural Geology of the Siyom Valley, Arunachal Pradesh - Surendra Singh and A. K. De