Abstract New Guinea has acted as the boundary between the Australian and Pacific plates for hundreds of millions of years. Strike-slip movement and arc–continent collisions along this boundary during the Cenozoic have shuffled rocks of different age and composition in a series of terranes along the plate boundary making mapping them a considerable challenge. Here we report results of Sr Nd isotopic data obtained from rock samples from western New Guinea that are representative of the different terranes. These isotopic data reveal the crustal affinity of the terranes and we have used these data to map their spatial distribution. The isotopic data show three distinct crustal domains underlying western New Guinea; Palaeozic–Mesozoic Australian continental crust (87Sr/86Sr = 0.719594 to 0.710921; eNd = −13.85 to 1.373); thinned transitional crust intruded by Miocene–Pleistocene magmatic rocks (87Sr/86Sr = 0.706524 to 0.704019; eNd = 6.67 to 2.13); and accreted island arc crust (87Sr/86Sr = 0.704053 to 0.703759; eNd = 6.63 to 4.97). These data, together with crustal contamination models, indicate that the northern-most extent of Australian continental crust exists beneath the northern-most section of western New Guinea. We also combined our isotopic data with existing data across New Guinea and used these to develop an isotopic map that shows the position of the ancient Australian–Pacific Plate boundary, producing results that are also consistent with broad-scale seismic tomography imagery. Our findings provide a framework for mapping other plate boundaries, particularly ancient systems where only fragmentary data exist.

中文翻译：

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同位素映射揭示了地壳碎片沿长寿命会聚板块边界的位置

摘要 数亿年来，新几内亚一直是澳大利亚板块和太平洋板块之间的分界线。新生代沿该边界的走滑运动和弧-陆碰撞使沿板块边界的一系列地体中不同年龄和成分的岩石发生了混洗，这使得对其进行测绘成为一项相当大的挑战。在这里，我们报告了从新几内亚西部岩石样本中获得的 Sr Nd 同位素数据的结果，这些岩石样本代表了不同的地体。这些同位素数据揭示了地体的地壳亲和力，我们已经使用这些数据绘制了它们的空间分布图。同位素数据显示了新几内亚西部下伏的三个不同的地壳域；古生代-中生代澳大利亚大陆地壳（87Sr/86Sr = 0.719594 至 0.710921；eNd = -13.85 至 1.373）；中新世-更新世岩浆岩侵入的变薄过渡地壳（87Sr/86Sr = 0.706524 to 0.704019; eNd = 6.67 to 2.13）；和增生岛弧地壳（87Sr/86Sr = 0.704053 至 0.703759；eNd = 6.63 至 4.97）。这些数据与地壳污染模型一起表明，澳大利亚大陆地壳的最北端存在于新几内亚西部最北端的下方。我们还将我们的同位素数据与新几内亚的现有数据相结合，并使用这些数据绘制了一幅同位素图，显示了古代澳大利亚 - 太平洋板块边界的位置，产生的结果也与大尺度地震断层扫描图像一致。我们的发现为绘制其他板块边界提供了一个框架，特别是只存在零碎数据的古代系统。