ベトナム,ランヴァク遺跡と出土青銅器の鉛同位体分析の結果について（2. 歴史資料産地決定法への適用 / [青銅器]）

ランヴァク遺跡は，ベトナムのゲアン省に所在するドンソン文化期，紀元前１～２世紀頃の遺跡である。この時代は，ちょうど日本の弥生時代のように，個性的な青銅器が発達し，鉄器の製作，使用も開始され，稲作を基礎とした社会が国家形成に向けて大きな変化を見せた時代である。1990～1991年ベトナム日本共同調査隊が行った発掘調査では，現在水田となっている谷をはさんで，東側の墓地遺跡（ランヴァク地点）と西側の集落址（ソムディン地点）が調査された。青銅器との関連で重要なことは，墓地遺跡で砂岩製の斧の鋳型が出土し，集落址では鋳型片や溶けた青銅の付着した土器から青銅器鋳造に使われたとみられる炉址が発見されたことである。ランヴァク遺跡はドンソン文化の広がりのなかではかなり南に位置し，ベトナム北部，中国南部ばかりでなく，ベトナム中・南部のサフィン文化やタイのバンチェン文化など周辺の広い地域との関連が見られる。ベトナムではこれまで鉛同位体の分析がおこなわれたことを聞かないが，今回のランヴァク資料の分析結果は，中国最南部の雲南や広西産の鉛の同位体比の範囲内に入るものであった。このことはランヴァクの青銅器が華南の原料で鋳造されたことを意味するかのごとくであるが，すぐにそう結論することはできない。中国のこの地域の青銅器については，主に戦国時代以後の銅鼓が鉛同位体分析の対象にとりあげられているが，その結果をみると，華北や四川省の殷周時代の青銅器とは異なり，地元の鉛との一致の傾向が顕著である。同じ状況がベトナムの青銅器についても当てはまるのかもしれない。ベトナム産鉛の同位体比の確認が緊急の課題である。今後南中国から東南アジア全体におよぶ広大な地域において青銅器原料の供給地と鋳造地の関係が解明されるなら，東南アジアにおける高文化の彩成過程の理解について，大きな前進となる。The Lang Vac sites of Dong Song cultural period, dated from 1-2 centuries B.C., are located in Nghe An Province, Vietnam. In this period, as like Yayoi period of Japan, characteristic bronze tools were developed and iron tools also began to be used, and the societies based on rice cultivation proceeded with the state formation. In 1990 and 1991, a joint research team of Vietnam and Japan excavated a cemetery site at Lang Vac location and a habitation site at Xom Dinh location of the Lang Vac site complex. The formar and the latter are located respectively on the eastern and western banks of a small valley presently used as paddy fields.Two important results were achieved for bronze analytical study. The one was discovery of several casting molds of sandstone for axes as well as many actual bronze tools such as daggers, spearheads, axes, bracelets, bells, and vessels from the burials of Lang Vac location. The other was excavation of two furnaces possibly for bronze casting judged by accompanied fragments of molds and a potsherd with adhered melt bronze at Xom Dinh location. In the whole area of Dong Song culture, Lang Vac sites are situated in its southern area, and multidirectional relationships can be recognized not only with northern Vietnam and southern China but also with Sahuynh culture of central to southern Vietnam, or with Banchiang culture of Thailand.The lead isotope ratios of bronze tools from Lang Vac location were within the extent of data group of Yunnan and Guangxi provinces, southern China. We cannot, however, rush to the conclusion that bronze tools of Lang Vac were made of raw materials procured in southern China. Bronze tools of Yunnan and Guangxi are known made of materials from mines in its vicinity. Same situation can be presumed for Vietnam, hence lead isotope ratios from Vietnamese ores are an urgent subject in order to define the provenance of materials used at Lang Vac sites.Bronze tools of Dong Song culture had close typological similarities with those of southern China and we can find similar ones, such as bronze drums of Heger I type, widely distributed in Southeast Asia also. Such phenomenon must have resulted from transportation of the products as well as from the diffusion of casting technique. Elucidated relationships between procurement sites and casting sites in the extensive area of Southeast Asia would surely through light upon the forming process of advanced societies in its late prehistory and early historic times