Time patterns of magmatic ore systems in circum-Pacific volcanoplutonic belts

Abstract

Integrate statistical processing of more than 1000 isotope dates tracing the history of circum-Pacific magmatic ore systems and related mineral deposits in volcanoplutonic belts allows the following inferences: (1) magmatic ore systems (MOS) of volcanic arcs generate monoand polycyclic volcanoplutonic deposits (VPD) with notably different formation times (longevities); (2) the MOS chronology bears periodicity of events in the post-Paleozoic history of the Pacific continental margin; (3) the time series of magmatic ore systems from different circum-Pacific segments show quasi-periodic patterns but the respective metallogenic epochs within the same time intervals have different phases and amplitudes, especially over the past 30 Myr; (4) each mineral type of VPD has its own periodicity; (5) the periodicity in formation times of mono- and polycyclic VPD differs from that in the times of their origin.

Dynamics of Convective Heat and Mass Transfer in Permeable Parts of Seismofocal Zones of the Kamchatka Region and Conjugated Volcanic Arcs

“…New geological and geophysical information about the structures of northwest part of PO, which appeared in the last two decades [16][17][18][19][20][21][22][23][24], contains the actual data, which has not received explanation in the framework of the discussion in the above review. Among them are research data that are not considered within the canonic model of subduction: (1) before the frontal part and in the rear area of the coastal stripe of volcanoes in the linear and arc permeable zones, there are cyclically occurring and ongoing processes of magmatism with certain geochemical trends [1, 5-7, 18, 25-28]; (2) in the northern and southern sectors of the Kuril-Kamchatka volcanic arc in the upper part of the lithosphere, there is a fixed splitting of the SFZ into the western and eastern branches with orthogonal drop of fracture zones [17,29] in the area of development of grouping (swarm) earthquakes [12,[30][31]; (3) central parts of volcanic arcs of the northern and northwest areas of PO fall into segments with different structural characteristics of transition zones and back-arc basins; (4) time harmonics of development of tectonic and magmatic processes [5,17] and stages of formation of PF deposits [2][3][4] allow assuming that within the seismic focal regions in the continental lithosphere, there have been previously and there are now permeable zones with periodically functioning mantle-crustal ore-magmatic systems. No correct physical models of heat-mass transfer have been proposed for such zones yet; (5) in these segments, there is no "frontal" volcanic zone, since magmatic and hydrothermal events have developed and still occur in the faults that are longitudinal and transverse to the axis of the ocean trench, in the strip of the modern subaerial volcanoes, considered to be the "frontal" volcanic area above the lithospheric wedge; and (6) there are latitudinal fault zones, in which all dated magmatic events in the interval 0-75 million years are recorded [6,18,26,28].…”

“…The last point is significant: the analysis of time harmonics of PF formation in the PO margins has found several characteristic dynamic features: (1) the existence of multistage mono-and polycyclic deposits [2][3][4] and (2) the duration of the formation of individual deposits ranges from a few tens of thousands of years to tens of millions of years, while maintaining thermodynamically close conditions of ore formation [1,5]. Over the observed period of less than 100 years within the SFZ of the Kamchatka region, the significant seismic activity has a cycle with a period of about 10-12 years [17].…”

“…Note the main structural and mineralogical and thermo-dynamic effects that may be assumed in the fields of compaction of heterophase media under volcanoes. The correct model of heat and mass transfer dynamics in orthomagmatic systems under volcanoes was developed [5,8], assuming the predominance of tension conditions in such systems [12]. This assumption was based on then available statistical data on the identified mechanisms of earthquakes [11][12].…”

“…At that, at the junction of blocks, there are regions with changing configuration, characterized by the conditions of compression. It is obvious that for such areas, the developed hydrodynamic model of magmatic fluid filtering [5,8] is not quite correct. Therefore, we are developing a more correct model of heat and mass transfer in compressible heterophase media as discussed below.…”

“…In the canonic model of these ore-forming systems, the fluid mass transfer is determined by the retrograde boiling of magma in mesoabyssal intrusive cameras. The analysis of time characteristics of formation [3,4] and the cyclic nature of porphyritic deposits of active margins of PO have showed that more than 70% of the described deposits are formed with the participation of mantle-crustal ore-magmatic systems [5]. Building quantitative models, it is necessary to rely on the data on tectonophysical characteristics of mantle-crust systems of modern volcanic arcs.…”