利用接收函数方法研究哀牢山剪切带南段金矿区的岩石圈结构: 岩石圈减薄与岩浆通道

印藏碰撞导致了青藏高原内部及周边地区形成巨量储量的成矿带。虽然这一地区的成矿研究非常深入，但仍然需要 完善对“源-运-储”的综合研究，需要从地壳上地幔结构角度对成矿源的起源进行探索。位于哀牢山剪切带南段的大坪- 长安金矿具有幔源成因迹象，该文研究了该矿区及邻区的岩石圈结构，从深部研究成矿来源。通过接收函数方法获得的研 究区剖面，揭示壳幔边界（Moho） 深度在30~40 km，但在金矿矿区下表现为Moho转换震相强烈横向不连续，表现为东西 两侧约3~5 km的下沉。岩石圈软流圈边界（LAB） 的转换震相揭示，研究区的岩石圈厚度为60~80 km，有效约束了研究区 强烈岩石圈减薄后剩余岩石圈的厚度。金矿区西侧思茅块体的岩石圈厚度最薄，位于前人层析成像工作揭示上地幔顶部一 低速体的上方。金矿区下方的岩石圈厚度为~80 km且LAB的转换震相表现为强烈的横向不连续。金矿下Moho和LAB的横 向不连续暗示了金矿区下方存在岩石圈尺度的岩浆通道，即软流圈的地幔物质可以较快速地到达浅表。笔者认为，研究区 的岩石圈结构支持由俯冲驱动的幔源成矿模型，但大坪-长安金矿矿区下的岩石圈尺度的岩浆通道的形成与哀牢山剪切带 的剪切变形直接相关。由Burma俯冲导致的地幔物质上涌对该通道的形成贡献有限。

The Lithospheric Structures Beneath the Au Deposits in the South Ailaoshan Shear Zone from Receiver Functions: Implications for Lithospheric Thinning and the Magma Channel

The Indo-Tibetan collision created the huge amounts of ore deposits in the Tibetan Plateau and around areas. Though these ore deposits have been well studied, it is still a challenge to link the reserve, the migration and the reserve together for an integrated analysis of the mineralization mechanism. Especially, it is still a gap to analyze the origin of the ore-forming materials in the crust-mantle scale. Thus, we use conversional seismic waves (i.e. receiver function technique) to study the lithospheric structures beneath the Daping-Chang’an Au deposits, which present strong evidence for mantle-induced origin, in the south segment of the Ailaoshan shear zone, southeastern margin of the Tibetan Plateau. We obtained a vertical section across the Au deposits region. The crust-mantle boundary (Moho) beneath the Au deposits is at 30-40 km depth while presents a clear sharp depression (~3-5 km) and complex waveforms. The lithosphere-asthenosphere boundary (LAB) on the section is at 60-80 km depth, constraining the thickness of the lithosphere after the strong thinning. The thinnest lithosphere is beneath the central Simao block and is above a low-velocity zone in the uppermost mantle from tomography. As well as the lateral discontinuity at the Moho beneath the deposits, the LAB beneath the deposits presents a significant lateral discontinuity, indicating lithospheric scale discontinuity. The lateral discontinuities at both the Moho and the LAB imply the magma channel, which could facilitate a quick migration of the magma from the asthenosphere to surface. We thought that the lithospheric structure beneath the Daping-Chang’an Au deposits supports the model of the subduction-induced mantle origin of the ore-forming materials. However, we thought that the shear of the Ailaoshan shear zone dominated the inferred lithospheric magma channel and that the subduction-induced upwelling of the mantle materials presented memorial contributions to the formation of the magma channel.