Multi-ring structures - new mapping techniques and their role in the mineral deposit localization

Category Mineral processing
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Gurevich, Dmitriy
Holding Date 03 September 2008

Multi-ring impact structures are known on at least seven planets and satellites. Their giant sizes (diameter can exceed 1500 km) and known examples of influence on mineral deposits localization stipulate task of identification of all major terrestrial multi-ring structures. There are some favorable preconditions for it.
1) multi-ring structures can be preserved for a long time due to influence on the shape and location of the consequent tectonic dislocations and intrusives.
2) external zones of the arc-form concentric dislocations, which are match wider then the central craters or calderas, can be efficiently used for the mapping of multi-ring objects on small-scale maps and images.
3) erosion emphasizes the fissured zones forming expressive relief multi-ring landforms.
Similar centrosimmetrical structures can be formed by endogenic processes, including: fracturing around volcanic crater, above the rising intrusion or the mantle plume, over the caldera-type collapse in the depleted magmatic reservoir.
At that endogenic structures can assimilate the shape and symmetry from more ancient ones endogenic or impact. Symmetry of the multi-ring structures overprinted on the heterogeneous substrate is connected with abruptness of the impact and/or increasing of the gomogenous properties down from the surface.
Data used in this study included independent and GIS-integrated analysis of various materials, as elevation models, river network, various scale geologic and geophysical maps, space images, deposits databases, author’s field observations. All of this allowed to specify sizes and structure of many known multi-ring structures and to reveal new ones.
Structure Luizi (13 km in diameter, southeast Congo), is considered as an example of a multi-ring structure of impact origin. Borovoe (60 km, North Kazakhstan) - an intrusive-related structure. Teniz (110 km, Central Kazakhstan) - a multi-ring structure which can be seen through overlying sediments. Structures located on the NW margin of the Okhotsko-Chukotsky vulcanic belt (Peschanka, Aniuy, Kupol) - example of interaction of semi-simultaneous intrusive-volcanic structures. Zhezkazgan (480 km, Central Kazakhstan) - a large negative structure with no clear origin. South-Ural (more than 180 km) - a multi-ring structure deformed by subsequent tectonic movements.
Preliminary analysis testifies that multi-ring structures are very common and include many linear dislocations as their components. They play important role in the mineral deposits localization. The following places were identified as favorable for deposit formation: intersection of the radial and ring faults (examples - gold deposits in the Borovoe structure, kimberlite pipes in Luizi crater); centre of the structure (Zhezkazgan Cu deposit); intersections of ring and radial faults of several structures (Kupol Au and Peschanka Cu); intersections of ring and regional faults (Sibay VMS).

 

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