3.0 Ga Thermo-tectonic Events Suffered by the 3.8 Ga Meta-quartz-diorite in the Anshan Area: Constraints from Apatite SHRIMP U-Th-Pb Dating
3.0 Ga Thermo-tectonic Events Suffered by the 3.8 Ga Meta-quartz-diorite in the Anshan Area: Constraints from Apatite SHRIMP U-Th-Pb Dating
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发表时间：
2007
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通讯作者：
Zhou Hongying
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作者：
Zhou Hongying
利用SHRIMP Ⅱ对鞍山地区3.8Ga变质石英闪长岩样品中的磷灰石进行了年龄测定。32次分析得到的207 Pb/206 Pb加权平均年龄为3007 ± 22 Ma，可解释为鞍山地区~ 3.0Ga强烈热构造事件中磷灰石的重结晶年龄。鞍山地区在3.0Ga以后发生了一系列地壳增生和其他热构造事件，但在3.8Ga的老岩石中至今未发现年龄小于3.0Ga的磷灰石。一般认为磷灰石的再结晶温度在400℃ ~ 500℃之间。因此，鞍山地区3.8Ga的老岩石自3.0Ga以来一直停留在岩石圈上部，从未下到13 km以上的深度。
An apatite sample separated from the 3.8 Ga (zircon SHRIMP U-Th-Pb age) meta-quartz-diorite sample in Anshan area has been dated using SHRIMP II. 32 analyses yielded a 207Pb/206Pb weighted mean age of 3007 ± 22 Ma that is interpreted as the age of recrystallization of the apatite during the very intense thermo-tectonic events at ~ 3.0 Ga in the Anshan area. In the Anshan area a series of crustal addition and other thermo-tectonic events took place after 3.0 Ga, however, no younger than 3.0 Ga apatite has been found in the 3.8 Ga old rock in the area so far. It is generally believed that the recrystallization temperature of apatite is between 400℃ and 500℃. Therefore it seems that the 3.8 Ga old rock in the Anshan area has always been staying in the upper lithosphere and never went down to the depth greater than 13 km since 3.0 Ga.