Thermochronological datasets for the Kyrgyz Tianshan and Siberian Altai-Sayan within Central Asia reveal a punctuated exhumation history during the Meso-Cenozoic. In this paper, the datasets for both regions are colle...Thermochronological datasets for the Kyrgyz Tianshan and Siberian Altai-Sayan within Central Asia reveal a punctuated exhumation history during the Meso-Cenozoic. In this paper, the datasets for both regions are collectively reviewed in order to speculate on the links between the Meso-Cenozoic exhumation of the continental Eurasian interior and the prevailing tectonic processes at the plate margins. Whereas most of the thermochronological data across both regions document late Jurassic -Cretaceous regional basement cooling, older landscape relics and dissecting fault zones throughout both regions preserve Triassic and Cenozoic events of rapid cooling, respectively. Triassic cooling is thought to reflect the Qiangtang-Eurasia collision and/or rifting/subsidence in the West Siberian basin. Alternatively, this cooling signal could be related with the terminal terrane-amalgamation of the Central Asian Orogenic Belt. For the Kygyz Tianshan, late Jurassic-Cretaceous regional exhumation and Cenozoic fault reactivations can be linked with specific tectonic events during the closure of the Palaeo-Tethys and Neo-Tethys Oceans, respectively. The effect of the progressive consumption of these oceans and the associated collisions of Cimmeria and India with Eurasia probably only had a minor effect on the exhumation of the Siberian Altai-Sayan. More likely, tectonic forces from the east （present-day co- ordinates） as a result of the building and collapse of the Mongol-Okhotsk orogen and rifting in the Baikal region shaped the current Siberian Altai-Sayan topography. Although many of these hypothesised links need to be tested further, they allow a first-order insight into the dynamic response and the stress propagation pathways from the Eurasian margin into the continental interior.展开更多
Fault-block structures of the Altay-Sayan folded area （ASFA） southeastern Siberia of Russia were used as the basis for creating a 3-D model. The surface structures were projected to depths by previous correlations b...Fault-block structures of the Altay-Sayan folded area （ASFA） southeastern Siberia of Russia were used as the basis for creating a 3-D model. The surface structures were projected to depths by previous correlations between long and deep faults, with all layers and deformation factors defined. The mean deformation factor （Ds） is 0.12 unit/km^3 in the upper layer, 0.012 unit/km^3 in the intermediate layer, and 0.007 unit/km^3 in the lower layer of the 3-D ASFA neotectonic model. Ds allows correlation of the three distinguished layers with theological bodies that differ in their potential for accumulating elastic energy. 3-D modeling can be used as a methodological approach to projections in seismic prone areas such as the Krasnoyarsk region, for earthquake-hazard monitoring.展开更多
Combustion metamorphic(pyrometamorphic)complexes produced by prehistoric natural coal fires are widespread inCentral Asia,namely at the interfaces between mountain systems and the flanking sedimentary basins.Large-sca...Combustion metamorphic(pyrometamorphic)complexes produced by prehistoric natural coal fires are widespread inCentral Asia,namely at the interfaces between mountain systems and the flanking sedimentary basins.Large-scale and prolonged firesaccompanied the initial orogenic stages as unweathered coal-bearing formations became exposed into the aeration zone.Pyrometamorphic rocks are comparable to sanidinite facies rocks in formation conditions and in alteration of sedimentary material but,unlike these,their protolith underwent different melting degrees to produce either ferrous basic paralavas or glazed clinkers.The phasecomposition of the newly-formed melted rocks are favorable for^(40)Ar/^(39)Ar dating of combustion metamorphic events which are coeval tothe onset of the main stage of recent orogenic events.We suggest a new algorithm providing correct ^(40)Ar/^(39)Ar dating ofpyrometamorphic rocks followed by well-grounded geological interpretation.We studied pyrometamorphic rocks in the western Salairzone of the Kuznetsk coal basin where combustion metamorphism under temperatures above 1000℃acted upon large volumes of coal-bearing sediments.Samples of paralavas were dated by the step heating ^(40)Ar/^(39)Ar method checked against internal(plateau andisochrone ages)and external('criterions of couple')mineralogical criterions,and against preliminary dating from geological andstratigraphic evidence.As a result,we distinguished two groups of dates for combustion metamorphic events.The first one(1.2±0.4Ma)is drawn towards the west boundary of Prokopyevsk-Kiselevsk block of Salair zone,while the second one(0.2±0.3Ma)isconfined to its east boundary.The former ages represent rocks in the western edge of the Prokopievsk-Kiselevsk block of the Salair zoneand the latter ages correspond to those in its eastern edge.The dates record the time when the fault boundaries of the blocks wererejuvenated during recent activity and the block accreted to the Salair orogenic area as a piedmont step.These are the first absolute agesobtained for the onset of uplift of the northern edge of the Ahai-Sayan area,the key event of its neotectonic history.The suggestedapproach to the choice of objects,classification of rocks,and interpretation of^(40)Ar/^(39)Ar data is universal and can be practiced in anyarea subjected to combustion metamorphism.展开更多
基金supported by grants from the Australian Research Council(DP150101730)the Fund for Scientific Research,FWO-Vlaanderen
文摘Thermochronological datasets for the Kyrgyz Tianshan and Siberian Altai-Sayan within Central Asia reveal a punctuated exhumation history during the Meso-Cenozoic. In this paper, the datasets for both regions are collectively reviewed in order to speculate on the links between the Meso-Cenozoic exhumation of the continental Eurasian interior and the prevailing tectonic processes at the plate margins. Whereas most of the thermochronological data across both regions document late Jurassic -Cretaceous regional basement cooling, older landscape relics and dissecting fault zones throughout both regions preserve Triassic and Cenozoic events of rapid cooling, respectively. Triassic cooling is thought to reflect the Qiangtang-Eurasia collision and/or rifting/subsidence in the West Siberian basin. Alternatively, this cooling signal could be related with the terminal terrane-amalgamation of the Central Asian Orogenic Belt. For the Kygyz Tianshan, late Jurassic-Cretaceous regional exhumation and Cenozoic fault reactivations can be linked with specific tectonic events during the closure of the Palaeo-Tethys and Neo-Tethys Oceans, respectively. The effect of the progressive consumption of these oceans and the associated collisions of Cimmeria and India with Eurasia probably only had a minor effect on the exhumation of the Siberian Altai-Sayan. More likely, tectonic forces from the east （present-day co- ordinates） as a result of the building and collapse of the Mongol-Okhotsk orogen and rifting in the Baikal region shaped the current Siberian Altai-Sayan topography. Although many of these hypothesised links need to be tested further, they allow a first-order insight into the dynamic response and the stress propagation pathways from the Eurasian margin into the continental interior.
文摘Fault-block structures of the Altay-Sayan folded area （ASFA） southeastern Siberia of Russia were used as the basis for creating a 3-D model. The surface structures were projected to depths by previous correlations between long and deep faults, with all layers and deformation factors defined. The mean deformation factor （Ds） is 0.12 unit/km^3 in the upper layer, 0.012 unit/km^3 in the intermediate layer, and 0.007 unit/km^3 in the lower layer of the 3-D ASFA neotectonic model. Ds allows correlation of the three distinguished layers with theological bodies that differ in their potential for accumulating elastic energy. 3-D modeling can be used as a methodological approach to projections in seismic prone areas such as the Krasnoyarsk region, for earthquake-hazard monitoring.
基金The study was supported by grant SS-4922. 2006. 5 from the president of the Russian Federation for leading science schools ("Siberian metamorphic school")grants 05-05-65036 from the Russian Foundation for Basic Researchit was carried out as part of Integration Project 105 of the Siberian Branch of the Russian Academy of Sciences.
文摘Combustion metamorphic(pyrometamorphic)complexes produced by prehistoric natural coal fires are widespread inCentral Asia,namely at the interfaces between mountain systems and the flanking sedimentary basins.Large-scale and prolonged firesaccompanied the initial orogenic stages as unweathered coal-bearing formations became exposed into the aeration zone.Pyrometamorphic rocks are comparable to sanidinite facies rocks in formation conditions and in alteration of sedimentary material but,unlike these,their protolith underwent different melting degrees to produce either ferrous basic paralavas or glazed clinkers.The phasecomposition of the newly-formed melted rocks are favorable for^(40)Ar/^(39)Ar dating of combustion metamorphic events which are coeval tothe onset of the main stage of recent orogenic events.We suggest a new algorithm providing correct ^(40)Ar/^(39)Ar dating ofpyrometamorphic rocks followed by well-grounded geological interpretation.We studied pyrometamorphic rocks in the western Salairzone of the Kuznetsk coal basin where combustion metamorphism under temperatures above 1000℃acted upon large volumes of coal-bearing sediments.Samples of paralavas were dated by the step heating ^(40)Ar/^(39)Ar method checked against internal(plateau andisochrone ages)and external('criterions of couple')mineralogical criterions,and against preliminary dating from geological andstratigraphic evidence.As a result,we distinguished two groups of dates for combustion metamorphic events.The first one(1.2±0.4Ma)is drawn towards the west boundary of Prokopyevsk-Kiselevsk block of Salair zone,while the second one(0.2±0.3Ma)isconfined to its east boundary.The former ages represent rocks in the western edge of the Prokopievsk-Kiselevsk block of the Salair zoneand the latter ages correspond to those in its eastern edge.The dates record the time when the fault boundaries of the blocks wererejuvenated during recent activity and the block accreted to the Salair orogenic area as a piedmont step.These are the first absolute agesobtained for the onset of uplift of the northern edge of the Ahai-Sayan area,the key event of its neotectonic history.The suggestedapproach to the choice of objects,classification of rocks,and interpretation of^(40)Ar/^(39)Ar data is universal and can be practiced in anyarea subjected to combustion metamorphism.
