| 大庙斜长岩同位素地质年龄、稀土地球化学及其地质意义 |
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| 引用本文： | 胡世玲,王松山,桑海清,裘冀,叶东虎,崔人合,戚长谋.大庙斜长岩同位素地质年龄、稀土地球化学及其地质意义[J].地质科学,1990,0(4):332-343. |
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| 作者姓名： | 胡世玲 王松山 桑海清 裘冀 叶东虎 崔人合 戚长谋 |
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| 作者单位： | 1. 中国科学院地质研究所;
2. 河北地质四队;
3. 长春地质学院 |
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| 摘 要： | 大庙斜长岩的40Ar/39Ar年龄测定呈现出一条典型的马鞍型年龄谱,在中温阶段有二个明显的坪年龄1656±15 Ma和1029±7 Ma,结合其构造位置和全球斜长岩分布来看,它们分别代表了侵位年龄和后期热扰动的时代。密云奥长环斑花岗岩中角闪石的40Ar/39Ar坪年龄为1716±21 Ma。两者时空上密切相关,代表了裂谷作用初期非造山环境中双模式岩浆作用产物。斜长岩类和苏长岩之间稀土配分模式的相似性表明,它们明显为同一成因的岩浆分异系列的产物。
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| 关 键 词： | 大庙斜长岩 斜长环斑花岗岩 40Ar/39Ar年龄 REE地球化学 裂谷作用 |
THE ISOTOPIC AGES AND REE GEOCHEMISTRY OF DAMIAO ANORTHOSITE AND THEIR GEOLOGICAL IMPLICATION |
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| Hu Shiling Wang Songshan Sang Haiqing Qiu Ji.THE ISOTOPIC AGES AND REE GEOCHEMISTRY OF DAMIAO ANORTHOSITE AND THEIR GEOLOGICAL IMPLICATION[J].Chinese Journal of Geology,1990,0(4):332-343. |
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| Authors: | Hu Shiling Wang Songshan Sang Haiqing Qiu Ji |
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| Institution: | 1. Institute of Geology, Academia Sinica, Beijing;
2. Geological Team No. 4, Hebei province;
3. Gelogical College of Changchun |
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| Abstract: | Damiao anorthosite is an unique massif type anorthosite in China, which emplaced into Archean gneisses and is closely associated with the Mijum rapakivi granite in space and time.The anorthosites are composed of anorthosite, monzonite and adamellite, and was intruded by norite dikes at late stage.The 40Ar/39Ar spectrum of unaltered dark anorthosite shows a typical saddle-shaped age spectrum, there are two remarkable plateau ages, 1029 ? 7 Ma (released 39Ar = 10%) and 1656 ?15 Ma (released 39Ar = 35%) in the middle temperture stage.The result of 1656 Ma plateau age is consistent with the age of Miyun rapakive granite (1716?21Ma 40Ar/39Ar plateau age, 1707?19Ma zircon U/Pb age, 1638 Ma K/Ar age) and also by the Bb/Sr and Sm/Nd isochron ages, 1686 Ma and 1735 Ma (Xia et al., 1986). Combined with the tectonic setting and world-wide occurrance of the anorthosites, this result is interpreted as an emplacement age The total fusion age of this sample, 2927-2952 Ma, and K/Ar age, 2939 and 3031 Ma, as well as the saddle-shaped spectrum as a whole demonstrate the existence of exsess Ar. The 1029 Ma plateau age is consistent with the emplacement age of late norite (1005 Ma, Rb/Sr isochron, 1076 Ma K/Ar age and 1065 Ma 40Ar/39Ar total fusion age), which represents the late thermal disturbance. In the case of Damiao anorthosites, based on the detailed field and geochronological studies, the two plateau ages are interpreted as two geological events.The similarity of REE abundance and pattern between the anorthostes and norite suggests the comagmatic differentiation series and common petrogenesis. The Sr isotope composition in Damiao anorthosites are laso within the range of major massif type anorthosites in the world.In sammary, the tectonic background, emplacement age and the rock suite of Damiao anorthosites show strong affinity to the world-wide anorthosite events (Karelian and Grenvill). It is of great importance for the evolution of Precambrian continental lithosphere. |
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| Keywords: | Damiao anorthosite rapakive granite massive type 40Ar/39Ar age Rb/Sr age REE geochemistry Rifting |
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