Tectonic controls of Mississippi Valley-type lead–zinc mineralization in orogenic forelands
Tectonic controls of Mississippi Valley-type lead–zinc mineralization in orogenic forelands
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DOI：
10.1007/s00126-003-0355-2
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发表时间：
2003-03
影响因子：
4.8
通讯作者：
D. Bradley;D. Leach
中科院分区：
文献类型：
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作者：
D. Bradley;D. Leach
世界上大多数密西西比河谷型（MVT）锌铅矿床产于造山前陆。我们研究构造方面的前陆演化的一部分，为什么一些前陆是丰富的MVT存款，而其他人是贫瘠的更广泛的研究。造山前陆的类型（碰撞型与安第斯型与反转型）不是一级控制，因为每个前陆都有MVT矿床（例如，分别是北方阿肯色州、松角和塞文）。在一些MVT地区（例如，三州和田纳西州中部），成矿作用发生在造山前隆顶部，这是一个低幅度（几百米），长波长（100-200公里）的隆起，由前陆板块的垂直加载形成。在活跃的班达弧碰撞区的前陆，一个不连续的前隆揭示了前隆环境的一些自然地理和地质复杂性，以及海平面在确定前隆是否会出现从而受到侵蚀方面的重要性。除了现存的前隆上的那些，一些MVT矿床直接出现在起源于前隆的不整合面之下，只是随后被板块构造输送带（例如，丹尼尔的港口和东田纳西州）。同样，一些矿床沿着碰撞前陆中的同碰撞、挠曲诱导的正断层和走滑断层（例如，北方阿肯色州、丹尼尔港和三州区）。这些发现揭示了岩石圈挠曲的重要性，并提出了一个概念性的构造模型，占一个重要的子集MVT存款的碰撞造山带的前沿。MVT矿床既出现在平坦地层中，也出现在逆冲断层地层中;在后一组地层中，在某些情况下，矿化发生在逆冲断层之后（例如，Picos de Europa），但在其他情况下可能早于逆冲作用（例如，东田纳西州）。
Most of the world's Mississippi Valley-type (MVT) zinc–lead deposits occur in orogenic forelands. We examine tectonic aspects of foreland evolution as part of a broader study of why some forelands are rich in MVT deposits, whereas others are barren. The type of orogenic foreland (collisional versus Andean-type versus inversion-type) is not a first-order control, because each has MVT deposits (e.g., Northern Arkansas, Pine Point, and Cevennes, respectively). In some MVT districts (e.g., Tri-State and Central Tennessee), mineralization took place atop an orogenic forebulge, a low-amplitude (a few hundred meters), long-wavelength (100–200 km) swell formed by vertical loading of the foreland plate. In the foreland of the active Banda Arc collision zone, a discontinuous forebulge reveals some of the physiographic and geologic complexities of the forebulge environment, and the importance of sea level in determining whether or not a forebulge will emerge and thus be subject to erosion. In addition to those on extant forebulges, some MVT deposits occur immediately below unconformities that originated at a forebulge, only to be subsequently carried toward the orogen by the plate-tectonic conveyor (e.g., Daniel's Harbour and East Tennessee). Likewise, some deposits are located along syn-collisional, flexure-induced normal and strike-slip faults in collisional forelands (e.g., Northern Arkansas, Daniel's Harbour, and Tri-State districts). These findings reveal the importance of lithospheric flexure, and suggest a conceptual tectonic model that accounts for an important subset of MVT deposits—those in the forelands of collisional orogens. The MVT deposits occur both in flat-lying and in thrust-faulted strata; in the latter group, mineralization postdated thrusting in some instances (e.g., Picos de Europa) but may have predated thrusting in other cases (e.g., East Tennessee).