Geochronological characteristics of the Guidong pluton and the Xiazhuang uranium ore-field
The Guidong plutonis a crucial part of the EW-directed Dadongshan-Guidong-Wuliting magmatic rock belt in the Nanling re-gion of South China.The Xiazhuang uranium orefield resides in the eastern portion of the Guidong pluton.Researchers have conducted extensive chronological testing on the Guidong pluton,the Xiazhuang uranium orefield,and their veins,obtaining abundant age data.This study synthesized the advances and characteristics of chronological research in the study area.The results show that:(1)The Guidong pluton is a complex pluton formed by Caledonian-Yanshanian magma at 450～151 Ma.From east to west,it can be divided in-to the Caledonian(450～418 Ma),the Indosinian(246～214 Ma),and the Yanshanian(189～151 Ma)plutons,manifesting a gradu-ally aging pattern from west to east.The Xiazhuang uranium orefield hosts NWW-,NEE-,and NNE-directedmafic veins form eddue to Yanshanian magmatism at 211～91 Ma.These veins can be categorized into five sets according to their ages:211～185 Ma,ca.180 Ma,145～139 Ma,110～100 Ma,and 93～91 Ma.The uranium mineralization in the orefield lasted from the middle Jurassic to the Miocene with an age of 175～20 Ma,involving five phases and six stages:The Middle Jurassic uranium mineralization(175～162 Ma),the late Jurassic-early Cretaceous uranium mineralization(138～123 Ma,113～100 Ma),the late Cretaceous uranium mineraliza-tion(96～66 Ma),the Paleocene uranium mineralization(65～54 Ma),and the Eocene-Miocene uranium mineralization and modifica-tion(52～20 Ma).Among them,138～123 Ma and 96～54 Ma constituted the primary mineralization epochs.(2)According to the chronological and geological data of the study area,the formation of the Guidong pluton and its uranium mineralization can be divided into the following eight phases and 12 stages.The first phase is the middle-late Caledonian magmatism(450～418Ma),forming subvol-canic and granitic rocks primarily in the northern and eastern peripheries of the Guidong pluton.The second phase is the Indosinian granitic magmatism(246～214 Ma),which was dominated by the granitic magmatism from the middle Triassic to the early stage of the late Triassic.The third phase is the early Yanshanian mafic magmatism and uranium mineralization(211～162 Ma),including three sta-ges:The mafic vein activity from the late stage of the Triassic to the early Jurassic(211～200 Ma),the early Jurassic granitic mag-matism(ca.180 Ma),and the middle Jurassic mafic vein activity and uraninite mineralization(179～162 Ma).The fourth phase is the Yanshanian magmatism(163～139 Ma),which formed the Yanshanian pluton in the west of the Guidong pluton,consists of the granit-ic magmatism during the late stage of the middle Jurassic(163～151 Ma)and the late Jurassic magmatism(145～39 Ma).The fifth phase is the late Yanshanian early Cretaceousuranium mineralization and mafic vein activity(138～100 Ma),which comprises the ura-nium mineralization at the early stage of the early Cretaceous(138～123 Ma)and the mafic vein activity and uraninite mineralization at the late stage of the early Cretaceous(113～100 Ma).The sixth phase is the late Yanshanian late Cretaceous uranium mineralization and mafic vein activity(96～66 Ma),serving as one primary mineralization phase.The seventh phase is the Himalayan Paleocene ura-nium mineralization(65～54 Ma).The eighth phase is the Himalayan Eocene-Miocene uranium mineralization and modification(52～20 Ma).3)The pluton formation and uranium mineralization are relatively concentratedin the study area,such as the Caledonian pluton(450～418 Ma),the Indosinian granitic pluton(238～220 Ma),the Yanshanian pluton(163～151 Ma),mafic vein activity(211～91 Ma),and uranium mineralization(138～123 Ma,96～54 Ma).There exists a certain time difference between uranium mineraliza-tion and granitic pluton formation,indicating that they are non-contemporaneous products.Each uranium mineralization was preceded by mafic vein activity,suggesting an intimate relationship between uranium mineralization and mafic vein activity.
Guidong plutonmafic veinXiazhuang uranium ore-fielddiagenetic agemetallogenic age
国家科技期刊平台
NSTL
万方数据
