云南中甸岛弧烂泥塘斑岩铜矿床岩体氧逸度特征及成矿意义
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摘要
烂泥塘斑岩铜矿床是义敦岛弧带南段(中甸岛弧)西斑岩成矿带新发现的中型铜矿床。针对烂泥塘斑岩铜矿床含矿石英二长斑岩和不含矿石英闪长玢岩、闪长玢岩的锆石Ce~(4+)/Ce~(3+)比值、δEu值以及氧逸度等特征进行研究,并通过计算得到2个含矿石英二长斑岩体Ce~(4+)/Ce~(3+)比值分别为294.85和283.31,δEu分别为0.72和0.77;不含矿的石英闪长玢岩和闪长玢岩Ce~(4+)/Ce~(3+)比值分别为105.63和87.07,δEu分别为0.73和0.36。表明与成矿有关的岩体具有相对较高的氧化状态。对比西藏冈底斯成矿带、云南金沙江-红河成矿带中段马厂箐铜钼矿和北段玉龙成矿带铜钼矿床岩体Ce~(4+)/Ce~(3+)比值,发现含矿岩体锆石的Ce~(4+)/Ce~(3+)比值通常都大于240,而不含矿岩体锆石的Ce~(4+)/Ce~(3+)比值都小于120(邦铺矿床除外)。并且可将锆石Ce~(4+)/Ce~(3+)>260、δEu>0.65参数作为烂泥塘斑岩型铜矿床成矿的地球化学标志。此外,烂泥塘矿区内含矿石英二长斑岩体的氧逸度(lg(fo_2))基本位于MH缓冲对之上,平均值分别为MH+2.1和MH+1.2,含矿斑岩体具有较高的氧逸度条件。锆石U-Pb年龄与锆石Ce~(4+)/Ce~(3+)比值以及氧逸度(lg(fo_2))存在负相关关系,表明复式岩体中晚阶段侵位的岩体更有利于成矿。
The zircon Ce~(4+)/Ce~(3+)ratios,δEu and oxygen fugacity of ore-bearing quartz monzonitic porphyry,barren quartz dioritic porphyrite and dioritic porphyrite of Lannitang porphyry copper deposit in south Yidun island arc(Zhongdian island arc)are investigated.It shows that the Ce~(4+)/Ce~(3+)ratios of two ore-bearing quartz monzonitic porphyry samples are 294.85 and 283.31 with the averages of 289.08 and theδEu in ores are 0.72 and 0.77 with the averages of 0.75.Meanwhile,the Ce~(4+)/Ce~(3+)ratios of barren quartz dioritic porphyrite and dioritic porphyrite sample are105.63 and 87.07 respectively with average of 96.36 and theδEu is 0.73 and 0.36 respectively with average of 0.54.It indicates that the mineralized intrusions have relatively higher oxidation state.Comparison of the Ce~(4+)/Ce~(3+)ratios of ore-bearing intrusions and barren intrusions with the Gangdese metallogenic belt of Tibet and with the Machangqing porphyry Cu-Mo deposit in central area of the Jinsha-Red River metallogenic belt and with the Yulong porphyry Cu-Mo belt in northern segment shows that the Ce~(4+)/Ce~(3+)ratios of ore-bearing intrusions are usually greater than 240,but the barren intrusions usually less than 120(Bangpu deposit exception).The value of Ce~(4+)/Ce~(3+)>260andδEu>0.65 from zircon can be used as the geochemical indicators for Lannitang porphyry copper deposits mineralization.In addition,the oxygen fugacity of ore-bearing quartz monzonitic porphyry(lg(fo_2))obtained by calculation of absolute oxygen from zircon Ce ratios and zircon Ti thermometer is basically located on the MH buffer with averages of MH+2.1and MH+1.2,indicating that the ore-bearing porphyry has higher oxidation state.The zircon UPb ages which have a negative correlation with the Ce~(4+)/Ce~(3+)ratios and the oxygen fugacity(lg(fo_2))demonstrate that in the late stage of emplacement of granite intrusions is more conducive to mineralization.
The zircon Ce~(4+)/Ce~(3+)ratios,δEu and oxygen fugacity of ore-bearing quartz monzonitic porphyry,barren quartz dioritic porphyrite and dioritic porphyrite of Lannitang porphyry copper deposit in south Yidun island arc(Zhongdian island arc)are investigated.It shows that the Ce~(4+)/Ce~(3+)ratios of two ore-bearing quartz monzonitic porphyry samples are 294.85 and 283.31 with the averages of 289.08 and theδEu in ores are 0.72 and 0.77 with the averages of 0.75.Meanwhile,the Ce~(4+)/Ce~(3+)ratios of barren quartz dioritic porphyrite and dioritic porphyrite sample are105.63 and 87.07 respectively with average of 96.36 and theδEu is 0.73 and 0.36 respectively with average of 0.54.It indicates that the mineralized intrusions have relatively higher oxidation state.Comparison of the Ce~(4+)/Ce~(3+)ratios of ore-bearing intrusions and barren intrusions with the Gangdese metallogenic belt of Tibet and with the Machangqing porphyry Cu-Mo deposit in central area of the Jinsha-Red River metallogenic belt and with the Yulong porphyry Cu-Mo belt in northern segment shows that the Ce~(4+)/Ce~(3+)ratios of ore-bearing intrusions are usually greater than 240,but the barren intrusions usually less than 120(Bangpu deposit exception).The value of Ce~(4+)/Ce~(3+)>260andδEu>0.65 from zircon can be used as the geochemical indicators for Lannitang porphyry copper deposits mineralization.In addition,the oxygen fugacity of ore-bearing quartz monzonitic porphyry(lg(fo_2))obtained by calculation of absolute oxygen from zircon Ce ratios and zircon Ti thermometer is basically located on the MH buffer with averages of MH+2.1and MH+1.2,indicating that the ore-bearing porphyry has higher oxidation state.The zircon UPb ages which have a negative correlation with the Ce~(4+)/Ce~(3+)ratios and the oxygen fugacity(lg(fo_2))demonstrate that in the late stage of emplacement of granite intrusions is more conducive to mineralization.
引文
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[15]Hoskin P,Schaltegger U.The composition of zircon and igneous and metamorphic petrogenesis[J].Zircon,2003,53:27-62.
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[17]罗茂澄,王立强,冷秋锋.邦铺钼(铜)矿床二长花岗斑岩、黑云二长花岗岩锆石Hf同位素和Ce4+/Ce3+比值[J].矿床地质,2011,30(2):266-277.
[18]Liang H Y,Ian H.Campbell,Charlotte Allen.Zircon Ce4+/Ce3+ratios and ages for Yulong ore-bearing porphyries in eastern Tibet[J].Miner Deposita,2006,41:152-159.
[19]胥磊落,毕献武,陈佑纬,等.云南金平铜厂斑岩铜钼矿区岩体锆石Ce4+/Ce3+比值及其对成矿的指示意义[J].矿物学报,2012,1:74-82.
[20]Trail D,Waston E B,Tailby N D.Ce and Eu anomalies in zircon as proxies for oxidation state of magmas[J].Geochimicaet Cosmochimica Acta,2012,97:70-87.
[21]Watson E B,Wark D A,Thomas J B.Crystallization thermometers for zircon and rutile[J].Contrib Mineral Petrol(Contributions to Mineralogy and Petrology),2006,151:413-433.
[22]凌洪飞.论花岗岩型铀矿床热液来源—来自氧逸度条件的制约[J].地质论评,2011,2:193-206.
1云南省地质调查院.云南香格里拉烂泥塘铜矿详查报告,2012.
[2]Ballard J R,Palin J M,Campbell I H.Relative oxidation states of magmas inferred from Ce(Ⅳ)/Ce(Ⅲ)in zircon:Application to porphyry copper deposits of northern Chile[J].Contributions to Mineralogy and Petrology,2002,144:347-364.
[3]曾普胜,王海平,莫宣学,等.中甸岛弧带构造格架及斑岩铜矿前景[J].地质学报,2004,25(5):535-540.
[4]侯增谦,杨岳清,曲晓明,等.三江地区义敦岛弧造山带演化和成矿系统[J].地质学报,2004,78(1):109-120.
[5]冷成彪,张兴春,王守旭,等.滇西北雪鸡坪斑岩铜矿S,Pb同位素组成及对成矿物质来源的示踪[J].矿物岩石,2008,28(4):80-88.
[6]费光春,李佑国,温春齐.四川乡城-稻城地区花岗岩地球化学特征及构造背景探讨[J].矿物岩石,2009,29(2):88-95.
[7]曾普胜,李文昌,王海平,等.云南普朗印支期超大型斑岩铜矿床:岩石学及年代学特征[J].岩石学报,2006,22(4):989-1 000.
[8]任江波,许继峰,陈建林,等.中甸岛弧成矿斑岩的锆石年代学及意义[J].岩石学报,2011,27(09):2 591-2 599.
[9]黄肖潇,许继峰,陈建林,等.中甸岛弧红山地区两期中酸性侵入岩的年代学、地球化学特征及成因[J].岩石学报,2012,28(5):1 493-1 506.
[10]费光春,赵发明,许家斌,等.藏北安多县白垩纪马凳火山岩地球化学特征及地质意义[J].矿物岩石,2004,34(1):46-51.
[11]Fei G C,Li Y G,Chen J.Zircon U-Pb geochronology and geochemistry of copper-bearing monzogranite in the Rexiang hydrothermal Cu deposite in the central Yidun Island Arc,northeastern Tibet[J].Geochemical Journal,2015,49:195-205.
[12]Qi L,Hu J,Gregoire D C.Determination of trace elements in granites by inductively coupled plasma mass spectrometry[J].Talanta,2000,51:507-513.
[13]Liu Y S,Hu Z C,Gao S,et al.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J].Chem Geol,2008,257:34-43.
[14]BOYNTON W V.Cosmochemistry of the rare earth elements:Meteorite studies[A].Henderson P.Rare Earth Element Geochemistry[C].Amsterdam:Elservier,1984,63-114.
[15]Hoskin P,Schaltegger U.The composition of zircon and igneous and metamorphic petrogenesis[J].Zircon,2003,53:27-62.
[16]辛洪波,曲晓明.西藏冈底斯斑岩铜矿带含矿岩体的相对氧化状态:来自锆石Ce(Ⅳ)/Ce(Ⅲ)比值的约束[J].矿物学报,2008,28(2):152-160.
[17]罗茂澄,王立强,冷秋锋.邦铺钼(铜)矿床二长花岗斑岩、黑云二长花岗岩锆石Hf同位素和Ce4+/Ce3+比值[J].矿床地质,2011,30(2):266-277.
[18]Liang H Y,Ian H.Campbell,Charlotte Allen.Zircon Ce4+/Ce3+ratios and ages for Yulong ore-bearing porphyries in eastern Tibet[J].Miner Deposita,2006,41:152-159.
[19]胥磊落,毕献武,陈佑纬,等.云南金平铜厂斑岩铜钼矿区岩体锆石Ce4+/Ce3+比值及其对成矿的指示意义[J].矿物学报,2012,1:74-82.
[20]Trail D,Waston E B,Tailby N D.Ce and Eu anomalies in zircon as proxies for oxidation state of magmas[J].Geochimicaet Cosmochimica Acta,2012,97:70-87.
[21]Watson E B,Wark D A,Thomas J B.Crystallization thermometers for zircon and rutile[J].Contrib Mineral Petrol(Contributions to Mineralogy and Petrology),2006,151:413-433.
[22]凌洪飞.论花岗岩型铀矿床热液来源—来自氧逸度条件的制约[J].地质论评,2011,2:193-206.
1云南省地质调查院.云南香格里拉烂泥塘铜矿详查报告,2012.
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