石英释光信号作为粉尘物源示踪手段的再研究

FURTHER INVESTIGATIONS OF QUARTZ LUMINESCENCE SIGNALS AS A TOOL FOR DUST SOURCE TRACING

石英释光灵敏度近年来已经在沉积物源区识别上展现出一定的应用潜力。为进一步认识可能影响石英释光灵敏度的因素,更加客观地评价其在物源示踪研究中的适用性,本文对中国北方东西部沙漠石英恒源光释光信号和线性调制光释光信号进行了组分分解,比较了东西部沙漠石英光释光组分的异同,并研究了不同组分信号对辐照-曝光以及快、中组分信号灵敏度对加热的响应。结果表明东西部沙漠的恒源光释光快、中组分衰减速率类似,但东部沙漠的快组分比例更高。东部沙漠线性调制光释光快、中组分峰值出现时间分别早于、晚于西部沙漠。辐照-曝光循环能够敏化东西部沙漠石英光释光快、中、慢3个组分。在加热敏化程度方面,西部沙漠快组分敏化要强于东部沙漠,而二者中组分具有类似的响应。根据光释光快组分在600～700℃的加热敏化特性可以将西部沙漠分为两组:一为塔克拉玛干、库姆塔格、巴丹吉林沙漠;二为古尔班通古特、腾格里、毛乌素沙漠,第二组与东部沙漠类似。

Quartz luminescence sensitivity has shown its potential applications to the study of sediment source tracing. However, rock formation and sedimentary processes both control quartz luminescence sensitivity, which may complicate its applications to sediment source tracing. This study applies luminescence components deconvoluted from 150 - 180μm quartz CW-OSL and LM-OSL signals to discriminate the difference between China＇s eastern and western deserts. The eastern deserts include Hulun Buir, Horqin and Otindag. The western deserts consist of Mu Us, Tengger, Badain Juran, Kumtag,Taklimakan and Gurbantungut. Decay rates of fast and medium components resolved from 40s CW-OSL show no systematic differences between eastern and western deserts. The decay rates of fast component are about 3.0s-^-1 , while decay rates of medium component are proximately 0. 3s-^-1. Slow components dominate the total 40s CW-OSL signals for both eastern and western deserts. However the relative contributions of fast component to 40s CW-OSL signals of western deserts are smaller than those of eastern desert. For 3000s LM-OSL,the maximum peak positions of fast OSL component of eastern deserts are smaller than those of western deserts. By contrast,the maximum peak positions of medium OSL component of eastern deserts are larger than those of western deserts. Component resolved luminescence sensitivity changes under irradiation-bleaching cycles and thermal annealing were analyzed using CW-OSL signals. In irradiation-bleaching cycles experiment, aliquots were first bleached for 40s using blue light, and then given a dose of 29.4Gy followed by 110℃ TL and OSL measurements. This procedure was repeated 20 times. All the OSL components are sensitized after 20 irradiation-bleaching cycles. However,the rank of most sensitized components varies among samples. Thermal sensitization experiment used aliquots which were first bleached using blue light for 40s and then heated to progressively higher temperatures from 200℃ to 700℃ in increments of 20℃ before administering a beta dose of 29.4Gy and measurements of 110℃ TL and OSL signals. Thermal sensitizations of OSL fast components of western deserts cause more than 150-fold enhancement except for the Mu Us sample. By contrast,Thermal sensitizations of OSL fast components of eastern deserts are less than 150 times. The thermal sensitizations of medium components are similar for both eastern and western deserts. According to the results of thermal sensitization characteristics of fast components between 600 -700℃ , the western deserts can be further divided into two subgroups, one of which includes Taklimakan, Kumtag and Badain Juran and the other consists of Gurbantungut, Tengger and Mu Us. The latter subgroup has similar thermal sensitization characteristics to those of eastern deserts.