粤中三水盆地构造-岩浆事件与矿集区形成

Study on the structural-magmatic events and the formation of ore deposits in the Sanshui basin,central Guangdong Province

粤中三水盆地喜山期银矿化粗面质凝灰岩中锆石LA-ICP-MSU-Pb年龄90～3175Ma。火山岩中锆石主要为其在形成及上升过程中捕获围岩中的碎屑锆石。火山岩中锆石U-Pb年龄表明粤中三水盆地基底含太古宙的残余锆石(2489Ma±30Ma,3175Ma±38Ma),华夏陆块元古宙基底存在与Grenville造山运动相对比的构造岩浆事件(955～1148Ma)及在新元古代(798Ma±12Ma,883Ma±10Ma)发生了较强烈的岩浆活动。粤中三水盆地经历了加里东期构造岩浆事件(438.0Ma±6.8Ma),之后至少经历了燕山早期(～160Ma)、燕山晚期(98.2Ma±1.1Ma)及喜山期3次构造岩浆事件。三水盆地多期次构造岩浆活动与成矿事件有一定的耦合关系,是控制矿床形成的主要因素。华南褶皱带岩浆活动强烈,经历新生代成矿作用,中新生代盆地边缘是找矿有利靶区。

Zircon LA-ICP-MS U-Pb age of the Cenozoic silver-bearing trachytic tuff from the Sanshui basin ranges from 90 to 3175 Ma. The zircon age of the Cenozoic volcanic rocks indicates that the zircon grains were captured during the formation and ascending of the volcanic melts. The occurrence of zircon grains with ages （2489 Ma±30 Ma,3175 Ma±38 Ma shows that the basement of the Shanshui basin contains the Archean relict zircon. The occurrence of zircon grains in Proterozoic age indicates that the Proterozoic basement of the Cathaysian block underwent structural-magmaic activities （955-1148 Ma） at the same period as the Grenville orogeny and the Neoproterozoic structural-magmatic activities （798 Ma±12 Ma, 883 Ma±10Ma）. The region of the Sanshui basin underwent Caledonian （438.0 Ma ±6.8 Ma）, early Yanshanian （-160 Ma）, late Yanshanian （±98.2±1.1Ma）, and Himalayan structural-magmatic events. The multi-structural magmatic events correlate well with the formation of deposits occurred in the southwestern rim of the Sanshui basin. It is concluded that the multi-structural-magmatic events are the key factors controlling the formation of the deposits in the southwestern rim of the Sanshui basin. The South China Fold belt underwent Himalayan ore-forming event and the rim regions of the faulted basins in the South China Fold Belt that underwent multi-structural-magmatic activities are favorable target area for mineral prospecting.