云南程海—宾川断裂带斑岩地球化学特征及成因

发布时间：2018-05-29 02:41

本文选题：斑岩 + 岩石成因　；参考：《昆明理工大学》2016年博士论文

【摘要】：程海—宾川断裂带位于扬子陆块西缘,属金沙江—红河构造带的重要组成部分之一,受印度—欧亚板块远程碰撞效应影响,沿该断裂带及其次级断裂分布着大量的新生代碱性斑岩。近年来,随着与富碱斑岩有关的找矿工作投入加大,程海—宾川构造岩浆带内,新发现了与永胜分水岭碱性侵入岩有关具中型规模找矿前景的铜矿床,在宾川小龙潭和大理笔架山富碱斑岩型铜金矿区也获得了重大找矿突破,两矿区有望达到中大型规模,引起了国内外地质学者的高度关注。与区内马厂箐铜钼金矿相比,该带内富碱岩浆演化机制和成岩动力学背景研究显得十分薄弱。本博士论文从区域地质背景分析入手,以分水岭、小龙潭和笔架山碱性侵入岩体为重点研究对象,在详细的岩石学、岩相学研究基础上,开展了较为系统的岩石地球化学(主量、微量和稀土元素)、锆石U-Pb年代学和Lu-Hf同位素等方面的研究,详细划分该构造岩浆带内富碱侵入岩的岩石类型,精确厘定了成岩年龄,深入探讨了岩石成因,构建了切合本区实际的成岩动力学模型。最后,简要分析了与典型矿区斑岩(马厂箐岩体)的成矿差异性原因。取得主要研究成果如下：(1)系统详细划分了研究区内碱性斑岩的岩石类型。岩石学和岩相学上,分水岭斑岩主要由(黑云母)花岗闪长斑岩、钾长花岗斑岩、闪长正长斑岩、二长斑岩和少量煌斑岩组成：小龙潭斑岩主要由二长花岗斑岩、(钾长)花岗斑岩、黑云母花岗闪长斑岩和黑云二长斑岩等组成;笔架山斑岩主要由石英二长斑岩、煌斑岩以及少量(钾长)花岗闪长斑岩组成。结合岩石地球化学特征,三个岩体则均是由长英质斑岩和煌斑岩组成。长英质斑岩虽在造岩矿物上有所不同,但结构特征相似,应为同源岩浆演化作用的结果；而煌斑岩在空间分布上显由南向北(距金沙江断裂距离由近及远),其规模和数量均呈递减趋势,可能与深部断裂通道和幔源镁铁质岩浆上升侵位距离有关。(2)详细分析了三个富碱侵入岩体的岩石地球化学特征。岩石地球化学特征显示,三个岩体长英质斑岩具富碱、富钾和准铝质—弱过铝质特征,属高钾钙碱性—钾玄岩系列岩石;具高Sr、高Sr/Y和(La/Yb)N匕值,低镁、Y和HREE特征,显较强的埃达克质岩石地球化学特征；LILE(Rb、Ba、U、Th和Sr)和LREE富集,Nb和Ti)亏损和显著的“TNT”负异常以及Eu弱或无负异常特征,反映源区岩浆具壳幔混合特征,其形成与俯冲环境有关。相似的微量和稀土元素组成及其配分模式,表明长英质斑岩属同源岩浆演化产物,有相同的源区特征和成岩环境。煌斑岩具富碱、高钾、低钛特征,属钾质—超钾质钙碱系列岩石,其稀土、微量元素特征与长英质斑岩相似,亦具“TNT”负异常,表明两者源区特征和成岩环境类似,但相近的∑REE含量,指明了两者源区和岩浆演化机制不同。(3)运用LA-ICP-MS锆石U-Pb法精确厘定了研究区斑岩的成岩年龄。应用锆石U-Pb法,获得3个岩体长英质斑岩成岩年龄整体介于35.6～34.5 Ma,煌斑岩成岩年龄为33.6 Ma,均处于青藏高原晚碰撞期(40～26 Ma)内。高度一致的成岩年龄,表明长英质斑岩和煌斑岩同属喜马拉雅期古近纪始新世晚期岩浆活动产物,两者具有相同的成岩动力学背景。(4)运用Lu-Hf同位素对研究区长英质斑岩源区组成进行了限定,并重新厘定了长英质斑岩的岩石成因类型。三个岩体长英质斑岩锆石具εHf(t)值负值多、正值少及对应的古老地壳二阶段模式年龄(672～1608 Ma)特点,表明中元古代古老地壳物质对其源区组分贡献较大,而幔源物质次之。结合岩相学和地球化学等指标,认为长英质斑岩应为具有C型埃达克质岩石地球化学特征的类I、S复合型富碱斑岩,其中不同岩体I型程度反映不同。(5)准确界定了研究区长英质斑岩岩浆形成温度。全岩锆石饱和温度计算结果,显示分水岭、小龙潭和笔架山长英质斑岩岩浆形成温度分别为730.02～785.30℃、757.86～789.01和748.75～778.68℃。相对一致的岩浆温度,表明它们起源位置大致相同；普遍较高的岩浆温度,反映幔源物质对岩浆源区不但贡献了物质组分还提供了热量。(6)深入分析了研究区长英质斑岩和煌斑岩的源区属性。研究成果表明,煌斑岩起源于受俯冲板片流体交代的含金云母尖晶石—石榴子石相二辉橄榄岩过渡相的岩石圈富集地幔低程度(2%～10%)部分熔融,源区深度约80 km。长英质斑岩起源于约53 km处的加厚下地壳底部,源区岩浆主要由石榴角闪岩相下地壳低程度(10%)部分熔融形成,同时源区还遭受了少量底侵而来的俯冲板片流体交代的岩石圈富集地幔熔融组分(煌斑岩岩浆)的混染,源区具显著的壳幔混合特征,与第4点锆石Hf同位素反映特征一致。(7)指出了研究区斑岩成岩动力学背景,构建了相应的成岩动力学模型。研究认为,长英质斑岩和煌斑岩均形成于印度—欧亚板块晚碰撞期力学性质由挤压向伸展转换背景下,与金沙江—红河富碱斑岩带形成背景一致。成岩动力学机制为：随着印度—欧亚板块进入晚碰撞期(40～26 Ma)构造应力由挤压转变为伸展,引起减压对流作用发生,诱发高温软流圈上涌加热岩石圈富集地幔发生部分熔融形成镁铁质(煌斑岩)岩浆,部分镁铁质熔体上升底侵加厚下地壳发生部分熔融并与之混染形成具壳幔混合特征的长英质岩浆。形成的镁铁质岩浆和长英质斑岩岩浆沿主碰撞期(65～41 Ma)产生的金沙江—红河走滑断裂、程海—宾川走滑断裂及其派生的次级断裂通道上升侵位形成煌斑岩和长英质斑岩。(8)分析了研究区三个斑岩体与马厂箐富碱斑岩矿化差异性原因。从产出构造位置、岩石特征、岩石地球化学特征和成岩年龄4个方面对比,认为研究区长英质斑岩矿化强度和规模弱小,可能受程海—宾川断裂带岩浆活动强度及其深部断裂通道连通性和岩浆分异程度等因素制约。
[Abstract]:The Cheng Hai Binchuan fault zone, located on the western margin of the Yangtze block, is one of the important parts of the Jinsha River Honghe tectonic belt, which is affected by the long-range impact of the India Eurasian plate. A large number of Cenozoic alkaline porphys are distributed along the fault zone and its secondary faults. In recent years, the prospecting work related to the alkali rich porphyry has increased. In the Hai Binchuan tectonic magma belt, a new copper deposit, which is related to the prospect of medium scale prospecting in the alkaline intrusive rocks of the Yongsheng watershed, has also been found. In the Binchuan Xiaolong Tan and the alkali rich porphyry copper gold mine of the Dali Beacon Hill, a major breakthrough has been obtained. The two mining area is expected to reach the medium and large scale model, which has aroused the high concern of the geologists at home and abroad. Compared with the Ma Changqing copper molybdenum gold deposit in the region, the research on the evolution mechanism of alkali rich magma and the dynamic background of diagenesis is very weak. This thesis begins with the analysis of regional geological background, focusing on the watershed, Xiaolong Tan and the alkaline intrusive rock mass of Beacon Hill, and has carried out the detailed petrology and petrography research. More systematic studies of Rock Geochemistry (principal, trace and rare earth elements), zircon U-Pb chronology and Lu-Hf isotopes have been studied in detail. The rock types of alkali rich intrusive rocks in the tectonic magma zone are detailedly divided, the age of diagenesis is determined accurately, petrogenesis is discussed in depth, and the actual diagenetic dynamic model of this area is constructed. Finally, The causes of metallogenic difference between the porphyry porphyry (MA Changqing rock mass) in typical mining area are briefly analyzed. The main achievements are as follows: (1) the rock types of alkaline porphyry in the study area are divided in detail. In petrology and petrography, the watershed porphyry is mainly composed of (Hei Yunmu) granodiorite, potassium long granite porphyry, diorite long porphyry, and two long. The porphyry is composed of a small number of porphyre: the Xiaolong Tan porphyry is mainly composed of two long granite porphyry, (potassium long) granite porphyry, black mica granodiorite porphyry and black cloud two long porphyry, and the Beacon Hill porphyry is composed mainly of quartz two porphyry, the porphyre and a small number of (potassium long) granodiorite porphyry. Combined with the geochemical characteristics of rock, three rock bodies are combined. The felsic porphyry is composed of the felsic porphyry and the porphyry. Although the felsic porphyry is different in rock forming minerals, the structure of the porphyry is similar, and it should be the result of the evolution of the homologous magma, while the spatial distribution of the porphyry is from the south to the North (far from the distance from the Jinsha River fault). The ascending emplacement distance of the channel and mantle derived mafic magma is related. (2) the rock geochemical characteristics of the three alkali rich intrusive rocks are analyzed in detail. The rock geochemical characteristics show that three pluton felsic porphyry is characterized by alkali rich, potassium rich and paralic - weak peraluminous characteristics, and is a high potassium calc alkaline - potassium basalt series rock; high Sr, high Sr/Y and (La/) Yb) N dagger value, low magnesium, Y and HREE characteristics, strong ADAC rock geochemical characteristics; LILE (Rb, Ba, U, Th and Sr) and LREE enrichment, Nb and significant negative anomalies and weak or unnegative anomalies, reflecting the mixture of crust and mantle of magma in the source region, which is related to the subduction environment. Similar trace and rare earth elements The composition and distribution pattern indicate that the felsic porphyry is a homologous magma evolution product, which has the same source area characteristics and diagenetic environment. The porphyry is characterized by alkali rich, high potassium and low titanium characteristics, and belongs to the potash ultralow calcite series rock. The rare earth and trace elements are similar to the felsic porphyry and have a negative TNT anomaly, indicating the characteristics of the two source regions and the characteristics of the two. The diagenetic environment is similar, but the similar content of the sigma REE indicates that the source area and the magma evolution mechanism are different. (3) using the LA-ICP-MS zircon U-Pb method to accurately determine the age of the diagenesis of the porphyry in the study area. By using the zircon U-Pb method, the age of the diagenesis of the 3 rock long feldspar porphyry is between 35.6 and 34.5 Ma, and the age of the porphyry is 33.6 Ma. In the late collision period of the Qinghai Xizang Plateau (40~26 Ma), the highly consistent diagenesis age indicates that the long felsic porphyry and the porphyry belong to the late Paleogene Eocene magma activity products of the Himalaya period, and they have the same diagenetic background. (4) the composition of the source area of the felsic porphyry in the study area was limited by the use of Lu-Hf isotopes. The petrogenetic types of the felsic porphyry are determined. The zircon of the three rocks of the felsic porphyry has more negative values of Hf (T), less positive value and corresponding age of the two stage model of the ancient crust (672~1608 Ma), indicating that the ancient crustal material of the Middle Proterozoic contributed to its source area larger, while the mantle source was second. It is considered that the felsic porphyry should be a kind of I and S complex alkali rich porphyry with the geochemical characteristics of the C type of the plex, and the degree of I type of different rock bodies is different. (5) the magma formation temperature of the felsic porphyry in the study area is accurately defined. The result of the full rock zircons saturation thermometer shows the watershed, the Xiaolong Tan and the Beacon Hill long feldspar. The formation temperature of porphyry magma is 730.02 ~ 785.30 C, 757.86 ~ 789.01 and 748.75 ~ 778.68 C. The relative uniform magma temperature shows that their origins are approximately the same, and the general high magma temperature shows that the mantle derived material not only contributed to the material component in the magma source area, but also provided the heat. (6) the deep analysis of the felsic substance in the study area was carried out. The source area of the porphyry and the porphyre shows that the porphyry originated from the low degree (2% to 10%) partial melting of the lithospheric enriched mantle with the transition phase of the gold mica spinel - pomegranite olidite from the subduction plate fluid. The source depth of the 80 km. long felsic porphyry originated from the thickened lower crust at about 53 km. The magma in the source area is mainly formed by partial melting of the low degree (10%) of the crust under the guava amphibolite facies. At the same time, the source area also suffers from a small amount of subducted subducted plate fluid metasomatism in the lithosphere enriched mantle melting component (the mantle magma). The source area is characterized by a significant mixture of crust and mantle, which is consistent with the characteristics of the fourth zircon Hf isotopes. (7) the diagenetic dynamic background of the porphyry in the study area is pointed out, and the corresponding diagenetic model is constructed. It is believed that the felsic porphyry and the porphyry are formed in the background of the mechanical properties of the India to Eurasian plate in the late collision period, which is consistent with the formation of the Jinsha River Honghe alkali rich porphyry zone. As the tectonic stress of the India Eurasian plate enters the late collision period (40~26 Ma), the tectonic stress is transformed from extrusion to extension, which causes the decompressed convection and induces the partial melting of the high temperature asthenosphere upwelling lithosphere enriched mantle to form the mafic magma, and the partial melting of the lower crust of the mfg melt and the partial melting of the lower crust. The mixed dyed and mixed staining forms the felsic magma with the mixture of crust and mantle. The mafic magma formed and the magma of the mafic magma and the felsic porphyry magma formed along the Jinsha River Honghe strike fault along the main collision period (65~41 Ma), and the zahai Binchuan strike slip fault and its derived secondary fault channels are ascending emplacement to form the porphyry and the felsic porphyry. (8) analysis The difference between the three porphyry rocks in the study area and the mineralization of the alkali rich porphyry in Ma Chang Qing. From the 4 aspects of the tectonic position, rock characteristics, rock geochemical characteristics and the age of diagenesis, it is considered that the mineralization intensity and size of the felsic porphyry in the study area are weak and small, which may be affected by the intensity of magmatic activity in the Cheng Hai Binchuan fracture zone and its deep fracture channel. Factors such as the degree of common and magmatic differentiation are restricted.
【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】：P588.13

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