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 theseore deposits have been well studied, it is still a challenge to link the reserve, the migration and the reserve together for an integratedanalysis of the mineralization mechanism. Especially, it is still a gap to analyze the origin of the ore-forming materials in thecrust-mantle scale. Thus, we use conversional seismic waves (i.e. receiver function technique) to study the lithospheric structuresbeneath the Daping-Chang’an Au deposits, which present strong evidence for mantle-induced origin, in the south segment of theAilaoshan shear zone, southeastern margin of the Tibetan Plateau. We obtained a vertical section across the Au deposits region. Thecrust-mantle boundary (Moho) beneath the Au deposits is at 30-40 km depth while presents a clear sharp depression (~3-5 km) andcomplex waveforms. The lithosphere-asthenosphere boundary (LAB) on the section is at 60-80 km depth, constraining the thickness ofthe lithosphere after the strong thinning. The thinnest lithosphere is beneath the central Simao block and is above a low-velocity zone inthe uppermost mantle from tomography. As well as the lateral discontinuity at the Moho beneath the deposits, the LAB beneath thedeposits presents a significant lateral discontinuity, indicating lithospheric scale discontinuity. The lateral discontinuities at both theMoho 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-inducedmantle origin of the ore-forming materials. However, we thought that the shear of the Ailaoshan shear zone dominated the inferredlithospheric magma channel and that the subduction-induced upwelling of the mantle materials presented memorial contributions tothe formation of the magma channel.