摘要:石榴子石U-Pb定年在限定金属矿床形成时代上具有一定的优越性，而且近年来得到不少成功地应用。作为长江中下游的重要组成部分，池州地区燕山期岩浆活动强烈，伴随有成矿作用。然而，由于矿体赋存于沉积围岩中，区内的铅锌矿化时代目前还很模糊。本次对许桥—乌谷墩铅锌矿中多条岩脉及石榴子石进行多种矿物原位U-Pb定年。乌谷墩矿区内见有两种岩性的岩脉，其一为闪长玢岩，与铜、钼矿化关系密切，锆石U-Pb定年结果为146～141 Ma；另一为细粒花岗岩，与钼矿化关系密切，锆石U-Pb定年结果为113.4±2 Ma。矽卡岩中石榴子石U-Pb定年结果为148～143 Ma，形成时代与闪长玢岩脉一致。根据现有数据，池州地区存在3个阶段的成岩成矿作用：第一阶段（150～135 Ma），主要形成中酸性侵入岩和与之相关的铜、金、钼、铅、锌等矿床；第二阶段（134～124 Ma），形成钾长花岗岩和相关的铅锌钼矿化；第三阶段（115～110 Ma），岩浆活动接近尾声，主要发育花岗岩脉，并伴随弱的钼矿化。结合区域成矿规律，池州地区的成矿作用不完全与长江中下游地区相同，且池州区内的多期Mo （W）矿化可能与中-新元古代增生地壳多阶段活化有关。
关键词: 石榴子石/
定年/
矽卡岩/
矿床/
长江中下游
Abstract:Garnet U-Pb dating has advantages in directly constraining the ore-formation age and has been successfully applied in recent years. As the important part of the Middle and Lower Yangtze River, the Chizhou area has experienced intensive Yanshanian magmatism, simultaneously accompanied by multi-period metal mineralization. Nevertheless, due to the ore bodies reserved in the surrounding sedimentary rocks, the time of Pb and Zn mineralization in the Chizhou area is still vague. Therefore, the in-situ U-Pb dating for zircon from dykes and garnet from skarn in the Xuqiao-Wugudun Pb-Zn deposit was carried out. In the Wugudun mining area, there are two types of magmatic dykes. One is diorite porphyries which closely related to Mo and Cu mineralization with ages ranging from 146～141 Ma and the other is fine-grained granites which closely related to Mo mineralization with age of 113.4±2 Ma. The garnet U-Pb dating gives results of 148～143 Ma which are consistent with the ages of diorite porphyries. Based on available data, there were three stages of diagenesis and mineralization in Chizhou area： the first stage （150～135 Ma） mainly generated intermediate-acid intrusions and associated deposits of Cu, Au, Mo, Pb and Zn. The second stage （134～124 Ma） formed K-feldspar granite and related Pb, Zn and Mo deposits. In the third stage （115～110 Ma）, the magmatic activity was near the end, and mainly produced some the granitic dykes, accompanied by weak Mo mineralization. Combined with regional metallogenic regularity, the mineralization in Chizhou area is not completely the same as that in the Middle and Lower Yangtze River, and the multi-phase Mo （W） mineralization in the Chizhou area may be related to the multi-stage activation of the Meso-Neoproterozoic accreted crust.
Key words:Garnet, Dating/
Skarn, Deposits/
The Middle and Lower Yangtze River/
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