砕屑岩研究の現状と21世紀への展望  [in Japanese] Perspective view of provenance studies on siliciclastic rocks for the 21st century  [in Japanese]

砕屑岩の組成から後背地の岩質と堆積盆をめぐる造構環境を復元する研究の現状と課題を総括した.モード組成は多様な情報をもたらす基本的な手法として重要で, かつ造構場の識別能力も高い.化学組成は分析の能率と客観性に利点があり, 希土類元素や微量元素をも活用することによって, 風化の見積りも含めた幅広い利用ができる.重鉱物や各種の鉱物についての粒子個々の化学組成や年代の情報は, 後背地についての一層深い理解をもたらす.このような各種の資料を一層多く集め, シーケンス層序学にもとづく地層の成因的な理解と結びつけて総合化することによって, 造構場や堆積環境, 後背地についての精度の高い復元をおこなうことができるようになる.

The present status of provenance study on clastic rocks was reviewed, and it was concluded that provenance studies with new tools and ideas are fruitful subjects in present and in future. Modal composition based on optical analysis is a primary data, but it is still most informative and important. Chemical analyses became another basic and important methods recently, because of its utility and convenience of instrument analysis such as XRF and ICP-MS. These data offer useful discriminating ways for provenance, tectonic setting and sedimentary environments. Heavy minerals also offer excellent information on provenance, using the data such as assemblage, chemistry, dating and isotope. These data should be synthesized with the framework of sequence stratigrapy in relation to sedimentary processes and environments.