TY - JOUR

T1 - Granitoid magmatism and metallogeny of the Lake Zone in Western Mongolia (by the example of the Bumbat-Hairhan area)

AU - Rudnev, S. N.

AU - Izokh, A. E.

AU - Borisenko, A. S.

AU - Gas'kov, I. V.

PY - 2016/2/1

Y1 - 2016/2/1

N2 - We present the results of a study of the geologic structure and age sequence of formation of the Late Neoproterozoic-Early Paleozoic plagiogranitoid and gabbroid associations in the Bumbat-Hairhan intrusive area of the Lake Zone in Western Mongolia. The petrogeochemical characteristics of the plagiogranitoids provide information about the conditions of formation of their parental melts at the island-arc and accretion-collision stages of the regional evolution. They also help to establish the main magma-generating sources as well as the major mechanisms of large-scale formation of granitoid melts and their relationship with ore generation processes. According to the trace-element and REE patterns and indicative ratios of these elements, the plagiogranitoids are subdivided into high- and low-alumina ones. Among the island-arc plagiogranitoids (551-524 Ma) of the Bumbat-Hairhan area, high-alumina varieties are the most widespread. They resulted from the partial melting of metabasites in equilibrium with garnet-containing restite at >. 15 kbar during their subsidence into the subduction zone. In geochemical features these plagiogranitoids are similar to high-Si adakites of different world regions. Island-arc low-alumina plagiogranitoids are scarcer. Their geochemical characteristics indicate that the parental melts were generated through the partial melting of metabasites in the lower part and/or in the basement of the island-arc system in equilibrium with amphibole-containing restite at <. 8 kbar. Plagiogranitoid associations of the accretion-collision stage (511-468 Ma) are the most widespread in the Bumbat-Hairhan area. They are subdivided into high- and low-alumina ones. According to the contents of trace elements and their indicative ratios, the low-alumina plagiogranitoids resulted from the partial melting of metabasites in equilibrium with plagioclase-containing restite at <. 8 kbar in the upper part of the collisional structure, and the high-alumina ones were generated through the melting of metabasites in the basement of thick crust in equilibrium with garnet-containing restite at >. 15 kbar. Geochronological studies in the Bumbat-Hairhan area revealed two stages of ore-generating processes spatially and temporally related to the formation of low-alumina plagiogranitoids. The early stage (518 ± 5 Ma), development of vein Cu (Au) mineralization, coincided in time with the formation of island-arc low-alumina plagiogranitoids of the Darbi massif (~. 524 Ma). The late stage (456 ± 4 Ma), formation of porphyry Cu-Mo (Au) mineralization, was synchronous with the formation of the low-alumina plagiogranites at the accretion-collision stage (~. 468 Ma).

AB - We present the results of a study of the geologic structure and age sequence of formation of the Late Neoproterozoic-Early Paleozoic plagiogranitoid and gabbroid associations in the Bumbat-Hairhan intrusive area of the Lake Zone in Western Mongolia. The petrogeochemical characteristics of the plagiogranitoids provide information about the conditions of formation of their parental melts at the island-arc and accretion-collision stages of the regional evolution. They also help to establish the main magma-generating sources as well as the major mechanisms of large-scale formation of granitoid melts and their relationship with ore generation processes. According to the trace-element and REE patterns and indicative ratios of these elements, the plagiogranitoids are subdivided into high- and low-alumina ones. Among the island-arc plagiogranitoids (551-524 Ma) of the Bumbat-Hairhan area, high-alumina varieties are the most widespread. They resulted from the partial melting of metabasites in equilibrium with garnet-containing restite at >. 15 kbar during their subsidence into the subduction zone. In geochemical features these plagiogranitoids are similar to high-Si adakites of different world regions. Island-arc low-alumina plagiogranitoids are scarcer. Their geochemical characteristics indicate that the parental melts were generated through the partial melting of metabasites in the lower part and/or in the basement of the island-arc system in equilibrium with amphibole-containing restite at <. 8 kbar. Plagiogranitoid associations of the accretion-collision stage (511-468 Ma) are the most widespread in the Bumbat-Hairhan area. They are subdivided into high- and low-alumina ones. According to the contents of trace elements and their indicative ratios, the low-alumina plagiogranitoids resulted from the partial melting of metabasites in equilibrium with plagioclase-containing restite at <. 8 kbar in the upper part of the collisional structure, and the high-alumina ones were generated through the melting of metabasites in the basement of thick crust in equilibrium with garnet-containing restite at >. 15 kbar. Geochronological studies in the Bumbat-Hairhan area revealed two stages of ore-generating processes spatially and temporally related to the formation of low-alumina plagiogranitoids. The early stage (518 ± 5 Ma), development of vein Cu (Au) mineralization, coincided in time with the formation of island-arc low-alumina plagiogranitoids of the Darbi massif (~. 524 Ma). The late stage (456 ± 4 Ma), formation of porphyry Cu-Mo (Au) mineralization, was synchronous with the formation of the low-alumina plagiogranites at the accretion-collision stage (~. 468 Ma).

KW - Central asian fold belt

KW - Geochemistry

KW - Geochronology

KW - Lake zone of Western Mongolia

KW - Late Neoproterozoic-Early Paleozoic intrusive magmatism

UR - http://www.scopus.com/inward/record.url?scp=84959365824&partnerID=8YFLogxK

U2 - 10.1016/j.rgg.2016.02.001

DO - 10.1016/j.rgg.2016.02.001

M3 - Article

AN - SCOPUS:84959365824

VL - 57

SP - 207

EP - 224

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 2

ER -