Reported in this paper are K-Ar dates of volcanic rocks, biotite-granite and greisen from Lianhuashan tungsten ore deposit in Guangdong Province. Isotopic dilution method is adopted in this work. The whole-rock isochr...Reported in this paper are K-Ar dates of volcanic rocks, biotite-granite and greisen from Lianhuashan tungsten ore deposit in Guangdong Province. Isotopic dilution method is adopted in this work. The whole-rock isochron ages of volcanic rocks are within the range of 120.4±12.1m.y. The petrogenetie age of biotlte-granite and the minerogenetic age of the tungsten ore deposit are close to those of the volcanic rocks. The apparent ages of various types of rocks in the mining district generally bias towards younger values, which may be attributed to the effects of late thermal events which took place in the eircum-Paeific mctallogenetic belt.展开更多
Six zircon smaples were collected from the Motianling massif. According to the characteristics of zircons, they were divided into three types and that of type Ⅲ were separated for isotopic age determination. Through ...Six zircon smaples were collected from the Motianling massif. According to the characteristics of zircons, they were divided into three types and that of type Ⅲ were separated for isotopic age determination. Through calculation and graphical analysis of the isotopic data on each zircon sample, true zircon ages were obtained:2860 m.y. for type Ⅰ, 760 m.y. for type Ⅱ and 510-580 m.y. for type Ⅲ, It is evident from geological environments of the Motianling massif, in conjunction with the characteristics of the zircons, that the first type formed earlier than the massif, the second one was contemperary with the massif, thus representing the age of the latter,and the third came into being due to metamorphism to which the massif had been subjected after its formation. From the above facts it is reasonable to believe that the Motianling massif is formed by granitization during the Xuefeng movement fromthe Sibao Group and the Banchi Group in the studied area. Later, it once again suffered metamorphism during the Caledonian movement and thus giving rise to the massif we observed at present.展开更多
26 determinations of the isotopic ages of granites and pegraatites by the K-Ar method are reported for the eastern section of the Eastern Tsinling. There may exist three periods of granites in this region, i.e., (1) l...26 determinations of the isotopic ages of granites and pegraatites by the K-Ar method are reported for the eastern section of the Eastern Tsinling. There may exist three periods of granites in this region, i.e., (1) late period of Early Paleozoie (420--450m.y.), (2) early period of Late Paleozoie (370-380m.y.)and (3) Mesozoic (178 m.y.) The granitic pegraatites are concentrated, in two regions-the eastern and the western regions. The western re,on is dated to be 400 m.y. Or more, and the eastern region, 370--380 m.y. Two samples of metamorphic rock from Ching-you-ho of Shangnan, Shensi and Lung-ehuan-ping of Lushi, Honan, are determined to be 451 and 453 m.y. respectively.展开更多
The principle, analytical procedures and applications of Rb-Sr dating for minerals and rocks are described. Sr was separated by ion exchange resin 71-616 (1) (made in China) and inorganic ion-exchanger ZrP (prepared i...The principle, analytical procedures and applications of Rb-Sr dating for minerals and rocks are described. Sr was separated by ion exchange resin 71-616 (1) (made in China) and inorganic ion-exchanger ZrP (prepared in our laboratory). All Sr determinations were made by isotope dilution and mass spectrometry. The concentration of Rb was analysed by flame spcetrophotometry. Rb-Sr ages of three micas (one from pegmatite from Inner Mongolia, and the other two are from granites from Kiangsi province) are in agreement with the K-Ar.rages and geological observations, indicating that the retention of radiogenic Sr^87 in micas is excellent. But systematic defferenee between K-Ar and Rb-Sr mica ages has been found in the other granite from Kiangsi province, suggesting possible eontaminations of radiogenic Sr^87 from magraas of different resources. Based on the isochrons formed by six total rocks and one feldspar, two metamorphie episodes of Jolmo Lungma series, Tibet, China (659±20, 17±6 m.y.) have been established. A similar conclusion has been reached by the U-Pb two stage model(modified eoncordia) ages, K-Ar dating as well as field investigations. It is believed that if sufficient geological data and suitable specimens are avilable, Rb-Sr isochron method may be a powerful toot to bring out multi-metamorphism in a given geological system.展开更多
文摘Reported in this paper are K-Ar dates of volcanic rocks, biotite-granite and greisen from Lianhuashan tungsten ore deposit in Guangdong Province. Isotopic dilution method is adopted in this work. The whole-rock isochron ages of volcanic rocks are within the range of 120.4±12.1m.y. The petrogenetie age of biotlte-granite and the minerogenetic age of the tungsten ore deposit are close to those of the volcanic rocks. The apparent ages of various types of rocks in the mining district generally bias towards younger values, which may be attributed to the effects of late thermal events which took place in the eircum-Paeific mctallogenetic belt.
文摘Six zircon smaples were collected from the Motianling massif. According to the characteristics of zircons, they were divided into three types and that of type Ⅲ were separated for isotopic age determination. Through calculation and graphical analysis of the isotopic data on each zircon sample, true zircon ages were obtained:2860 m.y. for type Ⅰ, 760 m.y. for type Ⅱ and 510-580 m.y. for type Ⅲ, It is evident from geological environments of the Motianling massif, in conjunction with the characteristics of the zircons, that the first type formed earlier than the massif, the second one was contemperary with the massif, thus representing the age of the latter,and the third came into being due to metamorphism to which the massif had been subjected after its formation. From the above facts it is reasonable to believe that the Motianling massif is formed by granitization during the Xuefeng movement fromthe Sibao Group and the Banchi Group in the studied area. Later, it once again suffered metamorphism during the Caledonian movement and thus giving rise to the massif we observed at present.
文摘26 determinations of the isotopic ages of granites and pegraatites by the K-Ar method are reported for the eastern section of the Eastern Tsinling. There may exist three periods of granites in this region, i.e., (1) late period of Early Paleozoie (420--450m.y.), (2) early period of Late Paleozoie (370-380m.y.)and (3) Mesozoic (178 m.y.) The granitic pegraatites are concentrated, in two regions-the eastern and the western regions. The western re,on is dated to be 400 m.y. Or more, and the eastern region, 370--380 m.y. Two samples of metamorphic rock from Ching-you-ho of Shangnan, Shensi and Lung-ehuan-ping of Lushi, Honan, are determined to be 451 and 453 m.y. respectively.
文摘The principle, analytical procedures and applications of Rb-Sr dating for minerals and rocks are described. Sr was separated by ion exchange resin 71-616 (1) (made in China) and inorganic ion-exchanger ZrP (prepared in our laboratory). All Sr determinations were made by isotope dilution and mass spectrometry. The concentration of Rb was analysed by flame spcetrophotometry. Rb-Sr ages of three micas (one from pegmatite from Inner Mongolia, and the other two are from granites from Kiangsi province) are in agreement with the K-Ar.rages and geological observations, indicating that the retention of radiogenic Sr^87 in micas is excellent. But systematic defferenee between K-Ar and Rb-Sr mica ages has been found in the other granite from Kiangsi province, suggesting possible eontaminations of radiogenic Sr^87 from magraas of different resources. Based on the isochrons formed by six total rocks and one feldspar, two metamorphie episodes of Jolmo Lungma series, Tibet, China (659±20, 17±6 m.y.) have been established. A similar conclusion has been reached by the U-Pb two stage model(modified eoncordia) ages, K-Ar dating as well as field investigations. It is believed that if sufficient geological data and suitable specimens are avilable, Rb-Sr isochron method may be a powerful toot to bring out multi-metamorphism in a given geological system.
