碎屑岩磷灰石单矿物多法定年进展与应用

A Review of Detrital Apatite Single-Grain LA-ICPMS Multi-Dating

沉积物是造山带-沉积盆地"从源到汇"过程中物质与能量交换的基本介质,同造山期沉积物岩屑单矿物多法定年是解译该过程最有效的半定量-定量手段。基于LA-ICPMS的磷灰石U-Pb和裂变径迹定年(磷灰石FT-U/Pb定年)是碎屑磷灰石单矿物原位多法定年的核心,它能够同时获得矿物结晶年龄和抬升冷却年龄等,从而能有效揭示盆-山系统中深层地壳-浅表作用的构造热事件过程。近年磷灰石FT-U/Pb年龄标样矿物系统的建立,204Pb、207Pb和208Pb普通Pb成分校正法的完善为磷灰石单矿物原位多法定年提供了越来越完善的理论基础,使其受到越来越广泛的重视与应用。磷灰石在沉积物"从源到汇"疏导过程中具有弱稳定性,代表着碎屑沉积物质首次剥蚀-沉积旋回过程,对于解译多旋回或复杂物源演化过程具有得天独厚的优势。对于缺少地层年代学限定的"从源到汇"过程,碎屑磷灰石多法定年不仅能够通过FT-U/Pb年代学限定地层沉积年龄,还可以通过时滞年龄曲线等获得造山带"源"-沉积盆地"汇"系统动态建造过程。磷灰石单矿物多法定年在解译盆-山耦合过程与机制的研究中发挥着越来越突出的作用。

Detrital materials are the basic medium in the source-to-sink processes from montain to basin,while this process could be deciphered by aquantitative method of detrital single-grain multi-dating.Apatite U-Pb and fission track dating（apatite FT-U/Pb dating）accomplished by laser ablation ICP-MS in single-grain is a key to the apatite single-grain multi-dating,which provides geochronology and thermochronolgy at the same times to unravel upper-crustal and near-surface processes.Recently,there are important progresses in the apatite standards,and common Pb correction by 204 Pb,207Pb,208Pb-methods.This means that U-Pb and Th-Pb dating of apatite potentially has broad application in sedimentary provenance studies,as it is likely to represent the first cycle detritus due to its limited mechanical stability in sedimentary transportation systems.Apatite FT-U/Pb ages could not only have wonderful constrains on the deposition age of host strata,in particular no reliable deposition age of terrestrial strata,but also unravel the thermal history of provenance and basin combined with lag-time model of cooling age and deposition age.Thus,apatite FT-U/Pb ages would have more and more applications in provenance and thermal history in a source to sink process.