Tin and Bronze Production in the Iron Age of Southern Africa

南非西北部的罗伊伯格山谷靠近博茨瓦纳边境，因其废弃的史前锡矿和冶炼锡的相关熔炉而闻名，这些熔炉将锡与铜合金制成青铜。当锡矿在20世纪初重新开始开采时，采矿工程师估计史前的锡矿产量约为2000吨。这是非洲南部唯一已知的锡或青铜生产实例，但在罗伊伯格进行了一个世纪的非系统研究后，基本问题仍未得到解答。锡矿开采是什么时候开始的？为什么？什么时候结束的，为什么？那么这里生产的大量锡去哪儿了呢？在美国国家科学基金会（National Science Foundation）的支持下，一个由美国、英国、南非和津巴布韦的研究人员组成的小组将在2006年通过一个实地挖掘季节开始研究这些问题。接下来将用一年的时间对挖掘出来的遗骸、之前挖掘出来的相关材料以及南非和津巴布韦的博物馆藏品进行深入的科学分析。现场工作将集中在冶炼场地的定位和挖掘上。我们预计最早的锡生产证据可以用放射性碳测定年代。然而，我们确实预计冶炼活动的高峰是从公元17世纪到19世纪初，这一时期的放射性碳定年法是不可用的。这一时期的遗址将通过光激发发光来确定年代，并通过使用考古磁力作为相对定年技术来支持。通过对出土遗骨的化学分析、金相学和薄片岩石学研究，对罗伊伯格河谷锡和青铜的生产工艺进行了重建。由于可以肯定的是，这里开采的大量锡并没有在Rooiberg地区被消耗掉（在整个假定的生产时期，该地区似乎人口稀少），这个项目的主要目的是为Rooiberg锡和铜矿石生产的锡和青铜开发微量元素和同位素指纹。采用等离子体质谱法测定出土锡、青铜中微量元素含量，采用高精度多收集器等离子体质谱法测定铅稳定同位素比值。该项目的最后阶段将是将路易堡锡和青铜的微量元素指纹与南非、博茨瓦纳和津巴布韦其他地方考古遗址的锡和青铜物品的微量元素指纹以及与南部非洲其他潜在矿石生产的锡进行比较。这些考古发现的年代从公元13世纪到19世纪不等，而发现地点距离罗伊堡最远700公里。因此，该项目的主要目的是记录南部非洲本土工业的出现及其产品通过的贸易网络的范围。该项目将为一名津巴布韦考古科学家提供宝贵的博士后培训，并为至少三名南非研究生和一名美国研究生提供博士前培训。

The Rooiberg valley in northwest South Africa, close to its border with Botswana, is notable for its abandoned prehistoric tin mines and associated furnaces for smelting tin, and for alloying tin with copper to make bronze. When tin mining was restarted here in the early 1900's, mining engineers estimated prehistoric production at about 2000 tons of tin metal. These are the only known instances of tin or bronze production in southern Africa, but after a century of unsystematic research at Rooiberg, basic questions remain unanswered. When did tin mining begin here, and why? When did it end, and why? And what happened to the large quantities of tin produced here? With National Science Foundation support, a team of American, British, South African and Zimbabwean researchers will begin to study these questions through one field season of excavations in 2006. This will be followed by a year of intensive scientific analysis of the excavated remains, and of related materials from prior excavations and museum collections in both South Africa and Zimbabwe. The fieldwork will concentrate upon locating and excavating smelting sites. We anticipate that the earliest evidence of tin production can be dated by radiocarbon. We do however expect that the peak of smelting activity was from the 17th through the early 19th centuries CE, a period in which radiocarbon dating is unusable. Sites in this period will be dated by optically-stimulated luminescence, backed up by the use of archaeomagnetism as a relative dating technique.The technology of tin and bronze production in the Rooiberg valley will be reconstructed by chemical analysis, metallography and thin-section petrography of the excavated remains. Since it is certain that the large quantity of tin mined here was not consumed in the Rooiberg area (which appears to have been lightly populated throughout the presumed time period of production) a major aim of this project is to develop trace element and isotopic fingerprints for tin and bronze produced from Rooiberg tin and copper ores. We will measure the concentrations of trace elements in excavated tin and bronze by plasma mass spectrometry, and the ratios of stable lead isotopes by high-precision multicollector plasma mass spectrometry. The final stage of the project will be to compare the trace element fingerprints for Rooiberg tin and bronze to those of tin and bronze objects from archaeological sites elsewhere in south Africa, Botswana and Zimbabwe, and to tin produced from other potential ores in southern Africa. The archaeological finds range in age from the 13th through the 19th centuries CE, while the find spots are up to 700 km distant from Rooiberg. Thus the main aim of the project is to document the emergence of an indigenous southern African industry and the extent of the trade network through which its products passed. The project will provide valuable postdoctoral training for a Zimbabwean archaeological scientists and predoctoral training for at least three graduate students from South Africa and one from America.