SHRIMP zircon U-Pb age of the fine-grained monzonitic granite in the Wulandele molybdenum-copper polymetallic ore deposit of Inner Mongolia and its significance
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摘要:
中蒙边境内蒙古苏尼特左旗乌兰德勒钼铜多金属矿床是内蒙古二连-东乌旗成矿带上新发现的一个规模较大的矿床。矿床地质特征研究表明,区内发育的隐伏细粒二长花岗岩与钼铜多金属矿床的形成有密切的时空、成因联系。为了揭示本区成矿规律,对细粒二长花岗岩进行了单颗粒SHRIMP锆石U-Pb测年,获得206Pb/238U年龄加权平均值为131.3±1.6Ma(MSWD=1.7),该年龄与矿石中的辉钼矿Re-Os同位素年龄134.1±3.3Ma基本一致,表明其形成时代为早白垩世。地质勘查成果表明,矿床的形成主要与隐伏的燕山期细粒二长花岗岩有着密切关系。上述同位素年龄的获得,为本区成矿规律的研究提供了重要依据。
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关键词:
- 细粒二长花岗岩 /
- 单颗粒锆石SHRIMP U-Pb年龄 /
- 乌兰德勒 /
- 中蒙边界
Abstract:The Wulandele molybdenum-copper polymetallic deposit in Sonid Left Banner of Inner Mongolia is a large deposit dis-covered recently during the geological survey in the Erlian-Dong Ujimqin Banner metallogenic belt of Inner Mongolia. Ore geology characteristics show that the formation of the molybdenum-copper polymetallic deposit had spatial-temporal and genetic relation-ships with the concealed fine-grained monzonitic granite in this area. In order to reveal the metallogenic regularity in this area, the authors determined the SHRIMP single particle zircon U-Pb age of the fine-grained monzonitic granite. The results show that the weighted average 206Pb/238U age of 131.3±1.6Ma(MSWD=1.7)is consistent with the molybdenite Re-Os age of 134.1±3.3Ma, sug-gesting that the formation age was Early Cretaceous. The result of geological exploration shows that the formation of the deposit was closely related to the concealed Yanshanian fine-grained monzonitic granite. The result of isotopic dating is important for the study of the regularity of ore formation.
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Key words:
- molybdenum-copper /
- SHRIMP zircon U-Pb age /
- Wulandele /
- Sino-Mongolian border
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表 1 乌兰德勒矿区二长花岗岩SHRIMP锆石U-Th-Pb同位素测定结果
Table 1. SHRIMP U-Th-Pb isotopic compositions of zircons in monzogranite from the Wulandele ore district
测点 206Pbc
/%U
/10-6Th
/10-6232Th
/238U206Pb*
/10-6206Pb/238U
年龄/Ma207Pb/206Pb
年龄/Ma208Pb/232Th
年龄/Ma207Pb*/235U 206Pb*/238U 207Pb*/206Pb* 比值 ±/% 比值 ±/% 比值 ±/% TW-1.1 1.39 196 128 0.67 4.38 163.4±3.1 278±190 168.8±9.6 0.1840 8.7 0.02568 1.9 0.0518 8.5 TW-2.1 0.68 2359 2785 1.22 41.6 130.1±2.0 162±53 127.1±2.3 0.1386 2.7 0.02038 1.6 0.0493 2.3 TW-3.1 10.65 694 585 0.87 14.6 139.6±3.2 1461±310 134±22 0.2770 17 0.02190 2.3 0.0920 16 TW-4.1 3.96 230 235 1.05 5.08 157.2±4.5 334±740 158±22 0.1810 33 0.02468 2.9 0.0530 33 TW-5.1 0.44 773 648 0.87 13.5 129.4±2.1 232±75 131.3±3.4 0.1421 3.6 0.02028 1.7 0.0508 3.2 TW-6.1 4.49 4250 3625 0.88 80.4 134.1±2.1 639±110 121.7±5.7 0.1767 5.2 0.02102 1.6 0.0610 5.0 TW-7.1 1.03 1632 1757 1.11 29.9 134.7±2.2 143±150 108.4±3.7 0.1424 6.6 0.02112 1.7 0.0489 6.4 TW-8.1 0.81 866 901 1.08 15.8 134.1±2.3 224±130 131.9±4.1 0.1467 5.8 0.02101 1.7 0.0506 5.6 TW-9.1 0.81 909 584 0.66 19.4 156.5±2.6 92±130 152.4±5.7 0.1622 5.6 0.02458 1.7 0.0478 5.4 TW-10.1 1.38 1630 1014 0.64 25.2 113.6±1.8 234±120 82.0±4.2 0.1246 5.5 0.01777 1.6 0.0508 5.3 TW-11.1 1.19 700 912 1.35 12.2 127.5±2.3 99±220 128.4±4.5 0.1320 9.4 0.01997 1.8 0.0480 9.3 TW-12.1 1.57 885 932 1.09 15.7 129.5±2.2 355±150 127.2±4.3 0.1500 7.0 0.02030 1.7 0.0536 6.8 注:206Pbc为普通铅;206Pb*为放射性铅。分析单位:中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室 -
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