Abstract Porphyry copper deposits are formed by fluids released from felsic magmatic intrusions of batholithic dimensions, which are inferred to have been incrementally built up by a series of sill injections. The growth of the magma chamber is primarily controlled by the volumetric injection rate from deeper-seated magma reservoirs, but can further be influenced by hydrothermal convection and fluid release. To quantify the interplay between magma chamber growth, volatile expulsion and hydrothermal fluid flow during ore formation, we used numerical simulations that can model episodic sill injections in concert with multi-phase fluid flow. To build up a magma chamber that constantly maintains a small region of melt within a period of about 50 kyrs, an injection rate of at least 1.3 x 10−3 km3/y is required. Higher magma influxes of 1.9 to 7.6 x 10−3 km3/y are able to form magma chambers with a thickness of 2 to 3 km. Such an intrusion continuously produces magmatic volatiles which can precipitate a copper ore shell in the host rock about 2 km above the fluid injection location. The steady fluid flux from such an incrementally growing magma chamber maintains a stable magmatic fluid plume, precipitating a copper ore shell in a more confined region and resulting in higher ore grades than the ones generated by an instantaneous emplacement of a voluminous magma chamber. Our simulation results suggest that magma chambers related to porphyry copper deposits form by rapid and episodic injection of magma. Slower magma chamber growth rates more likely result in barren plutonic rocks, although they are geochemically similar to porphyry-hosting plutons. However, these low-frequency sill injection events without a significant magma chamber growth can generate magmatic fluid pulses that can reach the shallow subsurface and are typical for high-sulfidation epithermal deposits.

中文翻译：

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岩浆房增量生长对斑岩铜系统成矿的作用

摘要 斑岩铜矿床是由基岩尺寸的长英质岩浆侵入体释放出的流体形成的，推测这些流体是通过一系列的基岩注入逐渐形成的。岩浆房的生长主要受来自深层岩浆储层的体积注入速率控制，但可以进一步受到热液对流和流体释放的影响。为了量化成矿过程中岩浆房生长、挥发物排出和热液流体流动之间的相互作用，我们使用了数值模拟，可以模拟与多相流体流动相一致的偶发性基石注入。为了建立一个在大约 50 kyrs 的时间内持续保持一小块熔体区域的岩浆房，至少需要 1.3 x 10−3 km3/y 的注入速率。更高的岩浆流入量 1.9 到 7。6 x 10−3 km3/y 能够形成厚度为 2 至 3 km 的岩浆房。这种侵入不断产生岩浆挥发物，可以在流体注入位置上方约 2 公里的主岩中沉淀出铜矿壳。来自这种逐渐增长的岩浆房的稳定流体通量保持着稳定的岩浆流体羽流，在更狭窄的区域沉淀出铜矿壳，并产生比瞬时侵位巨大岩浆房产生的矿石品位更高的矿石品位。我们的模拟结果表明，与斑岩铜矿床有关的岩浆房是由岩浆的快速间歇注入形成的。较慢的岩浆房生长速度更有可能导致贫瘠的深成岩，尽管它们在地球化学上类似于斑岩岩体。然而，