ESR/ICP-MS dating method of the latest fault movement

first,我们inspected the resetting state of ESR signals using the Nojima Fault 500m drilling核心样本，并确认在fault gouge之前已经完全删除了这一方法，即faultgouge samples as deep as possible are necessary for complete resetting of ESR signals. as a result计算机模拟on the decay process of ESR signals in the fault gouge，这是发现，我们应该作为一个resetting mechanism不只是frictional heat，但也有vaporization or convection of pore and crystal water in the fault gouge.Next我们已经做了关于fault gouge的chemical analysis in the 500m core samples to confirm whether ornot Pb anomaly actually存在. We analyzed by ICP-MS 8-20 μ m fractions separated from the bulksamples of the fault gouge. As a result we detected extreme - D1208 - D1Pb/ D1232 - D1Th andD1206 D1Pb/ D1238 D1U ratio anomalies from the 0-3mm part just on the fault plane. In the 0-3mmand 3-6mm parts of the fault gouge，the intensity of D1206 D1Pb/ D1238 D1U ratio is larger than that of D1208 D1Pb/ D1232 D1Thratio, whereas in the parts of more than 6mm away from the fault plane，D1Pb/ D1238 ratio D1U ratio is smaller than that ofD1208 D1Pb/ D1232 D1Th ratio. This suggests that the Pb anomaly may not be derived from themigration of the whole Pb isotopesbut from that of apart of D1206 D1Pb or D1208 D1Pb. The Pb anomaly may be explained by TheRn anomaly.Furthermore we experimentally generated fault gouge by hyirothermal reactionat high temperature and confirmed that smectites are ily generated in natural. One can evaluatefault activity by ESR dating of fault gouge using an intrinsic ESR signal in smectites. in addition，我们发现high energy particles irradiation a new ESR signal in quartz，which is applicable to ESR dating。

First, we inspected the resetting state of ESR signals using the Nojima Fault 500m drilling core samples, and confirmed that ESR signals in the fault gouge had been thermally reduced. This means that fault gouge samples as deep as possible are necessary for complete resetting of ESR signals. As a result of computer simulation on the decay process of ESR signals in the fault gouge, it was found that we should consider as a resetting mechanism not only frictional heat but also vaporization or convection of pore and crystal water in the fault gouge.Next, we carried out chemical analysis of the fault gouge in the 500m core samples to confirm whether or not Pb anomaly actually exists. We analyzed by ICP-MS 8-20 μ m fractions separated from the bulk samples of the fault gouge. As a result we detected extreme ィイD1208ィエD1Pb/ィイD1232ィエD1Th and ィイD1206ィエD1Pb/ィイD1238ィエD1U ratio anomalies from the 0-3mm part just on the fault plane. In the 0-3mm and 3-6mm parts of the fault gouge, the intensity of ィイD1206ィエD1Pb/ィイD1238ィエD1U ratio is larger than that of ィイD1208ィエD1Pb/ィイD1232ィエD1Th ratio, whereas in the parts of more than 6mm away from the fault plane, the intensity of ィイD1206ィエD1Pb/ィイD1238ィエD1U ratio is smaller than that of ィイD1208ィエD1Pb/ィイD1232ィエD1Th ratio. This suggests that the Pb anomaly may not be derived from the migration of the whole Pb isotopes, but from that of apart of ィイD1206ィエD1Pb or ィイD1208ィエD1Pb. The Pb anomaly may be explained by the existence of Rn anomaly.Furthermore we experimentally generated fault gouge by hyirothermal reaction at high temperature and confirmed that smectites are easily generated in natural. One can evaluate fault activity by ESR dating of fault gouge using an intrinsic ESR signal in smectites. In addition, we found by high energy particles irradiation a new ESR signal in quartz, which is applicable to ESR dating.