New monazite U\|Pb geochronological data from the Everest region suggest that 20～25Ma elapsed between the initial India—Asia collision and kyanite\|sillimanite grade metamorphism. Our results indicate a two\|phase m...New monazite U\|Pb geochronological data from the Everest region suggest that 20～25Ma elapsed between the initial India—Asia collision and kyanite\|sillimanite grade metamorphism. Our results indicate a two\|phase metamorphic history, with peak Barrovian metamorphism at (32 2±0 4)Ma and a later high\|temperature, low\|pressure event (620℃, 400MPa) at (22 7±0 2)Ma.. Emplacement and crystallization of the Everest granite subsequently occurred at 20 5～21 3Ma. The monazite crystallization ages that differ by 10Ma are recorded in two structurally adjacent rocks of different lithology, which have the same post collisional p—T history.. Scanning electron microscopy reveals that the younger monazite is elaborately shaped and grew in close association with apatite at grain boundaries and triple junctions, suggesting that growth was stimulated by a change in the fluid regime. The older monazite is euhedral, is not associated with apatite, and is commonly armoured within silicate minerals. During the low\|pressure metamorphic event, the armouring protected the older monazites, and a lack of excess apatite in this sample prevented new growth. Textural relationships suggest that apatite is one of the necessary monazite\|producing reactants, and spots within monazite that are rich in Ca, Fe, Al and Si suggest that allanite acted as a preexisting rare earth element host. We propose a simplified reaction for monazite crystallization based on this evidence.展开更多
Mt. Qomolangma (Everest), the highest mountain peak in the world, has little been studied extensively from a meteorological perspective, mostly because of the remoteness of the region and the re-sultant lack of meteor...Mt. Qomolangma (Everest), the highest mountain peak in the world, has little been studied extensively from a meteorological perspective, mostly because of the remoteness of the region and the re-sultant lack of meteorological data. An automatic weather station (AWS), the highest in the world, was set up on 27 April 2005 at the Ruopula Pass (6523 m asl) on the northern slope of Mt. Qomolangma by the team of integrated scientific expedition to Mt. Qomo-langma. Here its meteorological characteristics were analyzed according to the 10-minute-averaged and 24-hour records of air temperature, relative humidity, air pressure and wind from 1 May to 22 July 2005. It is shown that at 6523 m of Mt. Qomolangma, these meteorological elements display very obvious diurnal variations, and the character of averaged diurnal variation is one-peak-and-one-vale for air tem-perature, one-vale for relative humidity, two-peak-and- two-vale for air pressure, and one-peak with day-night asymmetry for wind speed. In the 83 days, all the air temperature, relative hu-midity and air pressure increased with some dif-ferent fluctuations, while wind speed decreased gradually and wind direction turned from north to south. The variations of relative humidity had great fluctuations and obvious local differences. Then thepaper discusses the reason for the characters of diurnal and daily variations. Compared with the corresponding records in May 1960, 5-day-averaged maximums, minimums and diurnal variations of air temperature in May 2005 were apparently lower.展开更多
In the summers of 2006 and 2007, the atmospheric CO 2 concentration and the wind speed in the Rongbuk Valley on the northern slope of Mt. Everest were measured by an ultrasonic anemometer with an Li-7500 CO 2 /H 2 O g...In the summers of 2006 and 2007, the atmospheric CO 2 concentration and the wind speed in the Rongbuk Valley on the northern slope of Mt. Everest were measured by an ultrasonic anemometer with an Li-7500 CO 2 /H 2 O gas analyzer. The average CO 2 concentration was 370.23±0.59 and 367.45±1.91 ppm in June of 2006 and 2007, respectively. The values are much lower than those at sites with similar latitudes and altitudes worldwide. The observed atmospheric CO 2 concentration in Rongbuk Valley can be affected by the transportation of prevailing down-valley winds from the up-valley direction to the observation site. Our results suggest that the Mt. Everest region could be ideal for background atmospheric and environmental studies.展开更多
文摘New monazite U\|Pb geochronological data from the Everest region suggest that 20～25Ma elapsed between the initial India—Asia collision and kyanite\|sillimanite grade metamorphism. Our results indicate a two\|phase metamorphic history, with peak Barrovian metamorphism at (32 2±0 4)Ma and a later high\|temperature, low\|pressure event (620℃, 400MPa) at (22 7±0 2)Ma.. Emplacement and crystallization of the Everest granite subsequently occurred at 20 5～21 3Ma. The monazite crystallization ages that differ by 10Ma are recorded in two structurally adjacent rocks of different lithology, which have the same post collisional p—T history.. Scanning electron microscopy reveals that the younger monazite is elaborately shaped and grew in close association with apatite at grain boundaries and triple junctions, suggesting that growth was stimulated by a change in the fluid regime. The older monazite is euhedral, is not associated with apatite, and is commonly armoured within silicate minerals. During the low\|pressure metamorphic event, the armouring protected the older monazites, and a lack of excess apatite in this sample prevented new growth. Textural relationships suggest that apatite is one of the necessary monazite\|producing reactants, and spots within monazite that are rich in Ca, Fe, Al and Si suggest that allanite acted as a preexisting rare earth element host. We propose a simplified reaction for monazite crystallization based on this evidence.
基金partially funded by the National Nature Science Foundation of China(Grant No.40501015)the Chinese Academy of Science(Grant No.KZCX3-SW-354 and KZCX3-SW-344).
文摘Mt. Qomolangma (Everest), the highest mountain peak in the world, has little been studied extensively from a meteorological perspective, mostly because of the remoteness of the region and the re-sultant lack of meteorological data. An automatic weather station (AWS), the highest in the world, was set up on 27 April 2005 at the Ruopula Pass (6523 m asl) on the northern slope of Mt. Qomolangma by the team of integrated scientific expedition to Mt. Qomo-langma. Here its meteorological characteristics were analyzed according to the 10-minute-averaged and 24-hour records of air temperature, relative humidity, air pressure and wind from 1 May to 22 July 2005. It is shown that at 6523 m of Mt. Qomolangma, these meteorological elements display very obvious diurnal variations, and the character of averaged diurnal variation is one-peak-and-one-vale for air tem-perature, one-vale for relative humidity, two-peak-and- two-vale for air pressure, and one-peak with day-night asymmetry for wind speed. In the 83 days, all the air temperature, relative hu-midity and air pressure increased with some dif-ferent fluctuations, while wind speed decreased gradually and wind direction turned from north to south. The variations of relative humidity had great fluctuations and obvious local differences. Then thepaper discusses the reason for the characters of diurnal and daily variations. Compared with the corresponding records in May 1960, 5-day-averaged maximums, minimums and diurnal variations of air temperature in May 2005 were apparently lower.
基金financed by the Chinese Academy of Sciences(Grant No.KZCX2-YW-Q11-01)the National Basic Research Program of China(Grant No.2009CB421403)
文摘In the summers of 2006 and 2007, the atmospheric CO 2 concentration and the wind speed in the Rongbuk Valley on the northern slope of Mt. Everest were measured by an ultrasonic anemometer with an Li-7500 CO 2 /H 2 O gas analyzer. The average CO 2 concentration was 370.23±0.59 and 367.45±1.91 ppm in June of 2006 and 2007, respectively. The values are much lower than those at sites with similar latitudes and altitudes worldwide. The observed atmospheric CO 2 concentration in Rongbuk Valley can be affected by the transportation of prevailing down-valley winds from the up-valley direction to the observation site. Our results suggest that the Mt. Everest region could be ideal for background atmospheric and environmental studies.
