The characteristic of microstructural deformation of gold bearing pyrite in Jiaodong: The links between nanoscale gold enrichment and crystal distortion

The model illustrating the pathway of the crystal concentrator on the gold distribution. The plastic-crystal distortion are resulted from gold and other trace elements homogeneously concentration, whereas pyrite crystal surface diffusion facilitates formation of gold nanoparticles by combining with many of these basic unit and promoting the formation of nanoparticle to discrete gold clusters in large pyrite grain. [Display omitted] •We combine SEM-FIB and TEM method to prove a large quantity of dislocation structures in auriferous pyrite.•The model has been built to explain the pathway from brittle-plastic crystal distortion structures of pyrite to gold concentration as impurity for invisible gold cluster and nanoparticle on deformed pyrite faces or lattices. Auriferous pyrite can host a large proportion of gold resource at giant gold deposits all around the world so that these sulfides minerals become key factors to reveal the genesis of ore deposits. In this paper, the focused ion beam-scanning electron microscope (FIB-SEM) method were conducted to present the in-situ transmission electron microscopy (TEM) high resolution images for dislocation ultrastructure study in auriferous pyrite. The TEM diffraction images evidences were provided to prove the evidence that gold cluster at the nanoscale could be existed among crystal interface or even crystal lattice (0.22 nm ~ 0.54 nm). Finally, we have proposed a model that link these nanostructures with gold concentration, gold aggregate in pyrite. The model illustrates the formation pathway of the of discrete invisible gold in pyrite grains which were controlled by shape and ultrastructure of pyrite crystalline, with ion-by-ion rapid diffusion on the surface or lattice. It’s well interpreting for inhomogeneous distribution of nanogold in pyrite resulted from combining with many of these basic pyrite units. In addition, it also reveals unique in-situ measurement result about crystal-fluid interface dynamic that identify the various lattice spacing with possibility for nanoparticle incorporation into deformed pyrite. This study not only provides a new insight into the interpretation of gold distribution and aggregation in pyrite that has significant indication for gold deposit formation in the world, but also provides important evidences for geochemical exploration for concealed deposits based on nanoscale gold.