云南祥云宝兴厂Cu、Mo矿区喜马拉雅期岩浆演化及成因
发布时间：2018-09-07 07:52
【摘要】：宝兴厂铜钼多金属矿床是金沙江-红河新生代斑岩成矿带中的重要矿区之一,矿区喜马拉雅期构造-岩浆活动强烈,发育不同类型富碱斑岩。本文对宝兴厂矿区开展了详细的野外地质调查及岩浆岩岩石学、岩石地球化学、成岩年代学及同位素地球化学等综合研究,取得以下主要成果：(1)用宏观地质体穿切关系与微观精确定年相结合的研究方法,重新厘定研究区岩浆侵位序列为正长斑岩(Ⅰ阶段)→斑状花岗岩+煌斑岩(Ⅱ阶段)→花岗斑岩+煌斑岩(Ⅲ阶段)→碱长花岗斑岩(Ⅳ阶段),证实矿区喜马拉雅斑岩体是同期多阶段岩浆脉动式活动的产物。其中,第Ⅱ阶段和第Ⅲ阶段为岩浆主要侵位期,均伴有不同程度的基性岩浆活动。(2)对已有可靠成岩年龄数据及本次新获得的LA-ICP-MS锆石U-Pb年龄数据的统计分析,确认矿区喜马拉雅期岩体形成年龄于38-33Ma之间,处在金沙江-红河富碱斑岩带的岩浆活动高峰期(45～30 Ma)范围内,但略滞后于其北段岩浆活动高峰期。区域构造-岩浆-成矿事件时空分布分析显示,沿金沙江-红河断裂带从北段的玉龙→中段北衙、宝兴厂→南段铜厂等,岩浆活动年龄和成矿年龄逐渐变新,反映青藏高原深部物质流动有向高原东南部迁移的趋势。(3)矿区喜马拉雅期花岗质岩浆活动由早阶段至晚阶段具有由中酸性→酸性,并向碱度增强和逐渐富钾方向演化的特点。其中,由早阶段岩体至晚阶段岩体,Si02含量具有逐渐增高的趋势,A1203、CaO、Fe203、MgO和P205的含量有逐渐变低的趋势,分异指数(DI)有逐渐增大的趋势,固结指数(SI)有逐步降低的趋势。暗色包体和煌斑岩的Si02含量在42.53%-54.98%之间,Si02、MgO、K20和全碱(K2O+Na2O)含量由早阶段煌斑岩+暗色包体→晚阶段煌斑岩依次升高,而A1203含量则依次降低。固结指数由暗色包体→早阶段煌斑岩→晚阶段煌斑岩逐渐增高,分异指数则相反且集中在40～50之间,暗示本区铁镁质岩浆岩结晶分异作用不强。其中,暗色包体和早阶段煌斑岩特征值相似或相近,揭示它们之间密切的演化关系。(4)不同阶段花岗质岩体、暗色包体和煌斑岩具相似的微量稀土元素特征：V、Co、Cu和Zn等过渡族元素轻微富集,Cr和Ni相对亏损,过渡族元素蛛网图均呈大致相同的“W”型,明显富集Rb、Ba、U、Th、Sr和La等大离子亲石元素(LILE)以及Nb、Ta(或“TNT”)异常亏损的特点。总体具有轻稀土富集、重稀土亏损,存在微弱δEu负异常的特点,其中花岗质岩体和晚阶段煌斑岩∑REE较低,暗色包体和早阶段煌斑岩∑REE较高。(5)煌斑岩、暗色包体及花岗质岩体具有相近的Sr、Nd、Hf同位素的组成：总体具有高Sr、低Nd的特征,但暗色包体和煌斑岩εNd(t)高于寄主花岗质岩体,显示幔源组分较高,具有向Ⅱ型富集地幔端元演化的趋势；寄主花岗质岩体的εHf(t)全部为正值,暗色包体和煌斑岩的εHf(t)均为负值,岩体高Hf和低Nd的特征,指示难熔的古老岩石圈地幔与俯冲的地壳物质相互作用的结果；矿区岩体Pb同位素组成具造山带铅特点,成因与壳-幔混合的岩浆作用有关；花岗质岩体的锆石的结晶标型揭示岩体在低温、偏碱环境下形成,且为以壳源为主的壳-幔混合成因,具有富水、富碱的特征,是利于成矿的岩浆系统；锆石总稀土含量很高,具有LREE强烈亏损、HREE富集的左倾配分型式,明显的正Ce异常,中等到弱的负Eu异常；锆石Hf同位素具有非常好的相似性,εHf(t)值散布于正值和负值(大部分为正值)之间,指示它们经历了比较显著的壳幔岩浆混合过程。因此,源区有显著的相关性又有区别,源区均具有俯冲板片流体交代富集地幔的特点,其中铁镁质岩浆主要起源于大陆岩石圈地幔,而花岗质岩浆源区主要起源于壳幔混合区。(6)宝兴厂矿区富碱侵入体形成于后碰撞的板内环境,构造-岩浆活动经历了以挤压向伸展转换过渡为主的减压升温过程,非常有利于发生基性到中酸性的岩浆演化以及大规模的岩浆-流体-成矿作用。矿区复式岩体经历源区部分熔融、壳幔混合以及结晶分异作用：花岗质侵入体和晚阶段煌斑岩为富集地幔源区相对高部分熔融(分别为15%和10%)的结果,暗色包体和早阶段煌斑岩为富集地幔源区低部分熔融(-3%)的产物；花岗质岩体地壳混染程度相对较高,煌斑岩混染程度相对较低；从花岗质侵入体→暗色包体→早阶段煌斑岩→晚阶段煌斑岩结晶分异程度依次升高；壳幔混合比例在0.44～0.60之间,主要集中在0.5附近。(7)矿区经历了地壳缩短加厚、软流圈上涌底侵、部分熔融和混合作用→热流升高、地壳减薄、壳幔混合的深部动力学作用过程,岩浆活动过程中产生流动分异和差异性上升,并沿红河断裂与程海断裂交汇处的局部引张区发生脉动式侵位,构成一个完整的构造-岩浆演化过程。据此,本文建立了陆内走滑动力学环境下岩浆脉动式侵位模型。模型指出：第1阶段岩浆岩的源区深度较大,源区的部分熔融程度较高,酸性组分和结晶分异程度较低,形成正长斑岩墙：第Ⅱ-Ⅲ阶段的岩浆的源区深度变浅,源区的部分熔融程度较低但规模大,有大量下地壳花岗质组分参与,酸性组分和结晶分异程度较高,依次形成与成矿有关的斑状花岗岩主岩体和含古老地壳基底物质的花岗斑岩岩枝(脉)；第Ⅳ阶段岩浆的源区深度与第Ⅱ-Ⅲ阶段相似,但源区的部分熔融程度最低,岩浆熔融规模小,分异程度高,仅形成岩墙状-脉状碱长花岗斑岩。岩浆主侵位阶段,还伴随有源区深度更大的小规模铁镁质岩浆侵入,形成矿区两阶段煌斑岩脉。
[Abstract]:Baoxingchang copper-molybdenum polymetallic deposit is one of the important ore-forming areas in Jinshajiang-Honghe Cenozoic porphyry metallogenic belt. The Himalayan tectonic-magmatic activities in the deposit are intense, and different types of ALKALI-RICH PORPHYRIES are developed. The main achievements are as follows: (1) The magmatic emplacement sequence in the study area is redefined as syenite porphyry (stage I) porphyry granite + lamprophyre (stage II) granite porphyry + lamprophyre (stage III) alkali feldspar granite porphyry by means of the combination of macroscopic geological body transection and microscopic precise dating. The Himalayan porphyry in the mining area is the product of multi-stage magmatic pulsation. The second and third stages are the main emplacement stages of magma, accompanied by different degrees of basic magmatic activity. (2) Statistical analysis of the available reliable diagenetic age data and the newly obtained LA-ICP-MS zircon U-Pb age data. The formation age of the Himalayan intrusive bodies in the mining area is 38-33Ma, which is within the peak period of magmatic activity (45-30 Ma) of the Jinshajiang-Honghe alkali-rich porphyry belt, but slightly lags behind the peak period of magmatic activity in the northern part of the belt. The magmatic age and metallogenic age of the northern Ya, Baoxingchang and southern Tongchang in the middle part of the Qinghai-Tibet Plateau are gradually renewed, reflecting the migration of the deep-seated material flow to the southeastern part of the plateau. (3) The Himalayan granitic magmatic activity in the mining area has a tendency from intermediate-acidic to acidic from the early stage to the late stage, and to the direction of increasing alkalinity and gradually enriching potassium. The content of Si02 increases gradually from early stage to late stage, A1203, CaO, Fe203, MgO and P205 decreases gradually, DI increases gradually, and SI decreases gradually. The content of Si02 in dark xenoliths and lamprophyres ranges from 42.53% to 54.98%. The contents of Si02, MgO, K20 and total alkali (K2O+Na2O) increase in turn from early stage lamprophyre + dark xenolith to late stage lamprophyre, while A1203 decreases in turn. The consolidation index increases gradually from dark xenolith to early stage lamprophyre to late stage lamprophyre, while the differentiation index is opposite and concentrates between 40 and 50, suggesting that the ferromagnesian magmatic rocks in this area are consolidated. The characteristics of dark xenoliths and early lamprophyres are similar or similar, which reveals their close evolutionary relationship. (4) In granitic rocks of different stages, dark xenoliths and lamprophyres have similar trace REE characteristics: slight enrichment of V, Co, Cu and Zn, relative depletion of Cr and Ni, and transition elements. The cobweb maps are generally of the same "W" type and are obviously enriched with Rb, Ba, U, Th, Sr and La and Nb, Ta (or "TNT") anomalous depletion. The cobweb maps are characterized by light rare earth enrichment, heavy rare earth depletion, and weak Delta Eu negative anomalies, including low REE in granitic rocks and late lamprophyres, dark xenoliths and dark xenoliths. The lamprophyre_REE is higher in the early stage. (5) Lamprophyre, dark xenoliths and granitic rocks have similar Sr, Nd, Hf isotope compositions. The characteristics of high Sr and low Nd are generally high, but the dark xenoliths and lamprophyres are higher than the host granitic rocks, indicating that mantle-derived compositions are higher and have a tendency to evolve toward type II enriched mantle end-member. The epsilon Hf (t) values of the granitic rocks are all positive, the epsilon Hf (t) values of the dark xenoliths and lamprophyres are negative, and the high Hf and low Nd characteristics of the rocks indicate the interaction between the refractory ancient lithospheric mantle and the subducted crustal materials. The crystalline TYPOMORPHISM OF ZIRCON in granitic intrusions reveals that the intrusions are formed under low temperature and alkaline environment, and are of crust-mantle mixing origin mainly derived from crust, which is characterized by water-rich and alkali-rich, and is favorable to the mineralization of magmatic systems; the total rare earth content of zircon is high, with strong LREE deficit, HREE enriched left-dip distribution pattern, and obvious positive Ce anomaly, intermediate to moderate. Weak negative Eu anomalies; zircon Hf isotopes have very good similarities, and the values of epsilon Hf (t) are scattered between positive and negative values (mostly positive), indicating that they have undergone a relatively significant crust-mantle magmatic mixing process. Medium-Fe-Mg magma mainly originated from the continental lithospheric mantle, while the granitic magma source mainly originated from the crust-mantle mixing area. (6) The alkali-rich intrusions in Baoxingchang mining area were formed in the post-collision intraplate environment, and the tectono-magmatic activities underwent a decompression-heating process mainly from compression to extension, which is very conducive to the occurrence of basic to intermediate acid. The complex intrusions experienced partial melting in the source area, crust-mantle mixing and crystallization differentiation: granitic intrusions and late-stage lamprophyres were the result of relatively high partial melting (15% and 10% respectively) in the enriched mantle source area, and dark xenoliths and early-stage lamprophyres were enriched. The products of low partial melting (-3%) in the source area of the mantle; the crustal contamination degree of granitic rocks is relatively high, while the lamprophyre contamination degree is relatively low; the crystalline differentiation degree of the lamprophyres from granitic intrusions to dark xenoliths to early lamprophyres to late lamprophyres increases in turn; the crust-mantle mixing ratio is between 0.44 and 0.60, mainly concentrated in 0.5 attachment. (7) The mining area has undergone the deep dynamic processes of crustal shortening and thickening, asthenospheric upwelling and underwelling, partial melting and mixing heat flow increasing, crust thinning, crust-mantle mixing, flow differentiation and differential ascension in the process of magmatic activity, and pulsating intrusion along the local extensional area at the intersection of Honghe fault and Chenghai fault. Based on this, a magma-pulsating emplacement model under the condition of intracontinental strike-slip mechanics is established. It is pointed out that the source area of the first stage magma is deep, the partial melting degree of the source area is high, the acidic component and the crystalline differentiation degree are low, and the syenite porphyry wall is formed: the second-third stage. The source area of the magma in the section becomes shallow, the partial melting degree in the source area is low but the scale is large, a large number of lower crustal granitic components are involved, the acidic components and crystalline differentiation degree are high, and the porphyry main body related to mineralization and the granite porphyry branch (vein) containing ancient crustal basement material are formed in turn. The depth of the area is similar to that of stage II-III, but the source area has the lowest degree of partial melting, small scale of magma melting and high degree of differentiation, forming only dike-vein alkaline feldspar porphyry.
【学位授予单位】：昆明理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.2
本文编号：2227659
[Abstract]:Baoxingchang copper-molybdenum polymetallic deposit is one of the important ore-forming areas in Jinshajiang-Honghe Cenozoic porphyry metallogenic belt. The Himalayan tectonic-magmatic activities in the deposit are intense, and different types of ALKALI-RICH PORPHYRIES are developed. The main achievements are as follows: (1) The magmatic emplacement sequence in the study area is redefined as syenite porphyry (stage I) porphyry granite + lamprophyre (stage II) granite porphyry + lamprophyre (stage III) alkali feldspar granite porphyry by means of the combination of macroscopic geological body transection and microscopic precise dating. The Himalayan porphyry in the mining area is the product of multi-stage magmatic pulsation. The second and third stages are the main emplacement stages of magma, accompanied by different degrees of basic magmatic activity. (2) Statistical analysis of the available reliable diagenetic age data and the newly obtained LA-ICP-MS zircon U-Pb age data. The formation age of the Himalayan intrusive bodies in the mining area is 38-33Ma, which is within the peak period of magmatic activity (45-30 Ma) of the Jinshajiang-Honghe alkali-rich porphyry belt, but slightly lags behind the peak period of magmatic activity in the northern part of the belt. The magmatic age and metallogenic age of the northern Ya, Baoxingchang and southern Tongchang in the middle part of the Qinghai-Tibet Plateau are gradually renewed, reflecting the migration of the deep-seated material flow to the southeastern part of the plateau. (3) The Himalayan granitic magmatic activity in the mining area has a tendency from intermediate-acidic to acidic from the early stage to the late stage, and to the direction of increasing alkalinity and gradually enriching potassium. The content of Si02 increases gradually from early stage to late stage, A1203, CaO, Fe203, MgO and P205 decreases gradually, DI increases gradually, and SI decreases gradually. The content of Si02 in dark xenoliths and lamprophyres ranges from 42.53% to 54.98%. The contents of Si02, MgO, K20 and total alkali (K2O+Na2O) increase in turn from early stage lamprophyre + dark xenolith to late stage lamprophyre, while A1203 decreases in turn. The consolidation index increases gradually from dark xenolith to early stage lamprophyre to late stage lamprophyre, while the differentiation index is opposite and concentrates between 40 and 50, suggesting that the ferromagnesian magmatic rocks in this area are consolidated. The characteristics of dark xenoliths and early lamprophyres are similar or similar, which reveals their close evolutionary relationship. (4) In granitic rocks of different stages, dark xenoliths and lamprophyres have similar trace REE characteristics: slight enrichment of V, Co, Cu and Zn, relative depletion of Cr and Ni, and transition elements. The cobweb maps are generally of the same "W" type and are obviously enriched with Rb, Ba, U, Th, Sr and La and Nb, Ta (or "TNT") anomalous depletion. The cobweb maps are characterized by light rare earth enrichment, heavy rare earth depletion, and weak Delta Eu negative anomalies, including low REE in granitic rocks and late lamprophyres, dark xenoliths and dark xenoliths. The lamprophyre_REE is higher in the early stage. (5) Lamprophyre, dark xenoliths and granitic rocks have similar Sr, Nd, Hf isotope compositions. The characteristics of high Sr and low Nd are generally high, but the dark xenoliths and lamprophyres are higher than the host granitic rocks, indicating that mantle-derived compositions are higher and have a tendency to evolve toward type II enriched mantle end-member. The epsilon Hf (t) values of the granitic rocks are all positive, the epsilon Hf (t) values of the dark xenoliths and lamprophyres are negative, and the high Hf and low Nd characteristics of the rocks indicate the interaction between the refractory ancient lithospheric mantle and the subducted crustal materials. The crystalline TYPOMORPHISM OF ZIRCON in granitic intrusions reveals that the intrusions are formed under low temperature and alkaline environment, and are of crust-mantle mixing origin mainly derived from crust, which is characterized by water-rich and alkali-rich, and is favorable to the mineralization of magmatic systems; the total rare earth content of zircon is high, with strong LREE deficit, HREE enriched left-dip distribution pattern, and obvious positive Ce anomaly, intermediate to moderate. Weak negative Eu anomalies; zircon Hf isotopes have very good similarities, and the values of epsilon Hf (t) are scattered between positive and negative values (mostly positive), indicating that they have undergone a relatively significant crust-mantle magmatic mixing process. Medium-Fe-Mg magma mainly originated from the continental lithospheric mantle, while the granitic magma source mainly originated from the crust-mantle mixing area. (6) The alkali-rich intrusions in Baoxingchang mining area were formed in the post-collision intraplate environment, and the tectono-magmatic activities underwent a decompression-heating process mainly from compression to extension, which is very conducive to the occurrence of basic to intermediate acid. The complex intrusions experienced partial melting in the source area, crust-mantle mixing and crystallization differentiation: granitic intrusions and late-stage lamprophyres were the result of relatively high partial melting (15% and 10% respectively) in the enriched mantle source area, and dark xenoliths and early-stage lamprophyres were enriched. The products of low partial melting (-3%) in the source area of the mantle; the crustal contamination degree of granitic rocks is relatively high, while the lamprophyre contamination degree is relatively low; the crystalline differentiation degree of the lamprophyres from granitic intrusions to dark xenoliths to early lamprophyres to late lamprophyres increases in turn; the crust-mantle mixing ratio is between 0.44 and 0.60, mainly concentrated in 0.5 attachment. (7) The mining area has undergone the deep dynamic processes of crustal shortening and thickening, asthenospheric upwelling and underwelling, partial melting and mixing heat flow increasing, crust thinning, crust-mantle mixing, flow differentiation and differential ascension in the process of magmatic activity, and pulsating intrusion along the local extensional area at the intersection of Honghe fault and Chenghai fault. Based on this, a magma-pulsating emplacement model under the condition of intracontinental strike-slip mechanics is established. It is pointed out that the source area of the first stage magma is deep, the partial melting degree of the source area is high, the acidic component and the crystalline differentiation degree are low, and the syenite porphyry wall is formed: the second-third stage. The source area of the magma in the section becomes shallow, the partial melting degree in the source area is low but the scale is large, a large number of lower crustal granitic components are involved, the acidic components and crystalline differentiation degree are high, and the porphyry main body related to mineralization and the granite porphyry branch (vein) containing ancient crustal basement material are formed in turn. The depth of the area is similar to that of stage II-III, but the source area has the lowest degree of partial melting, small scale of magma melting and high degree of differentiation, forming only dike-vein alkaline feldspar porphyry.
【学位授予单位】：昆明理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.2
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