| 其他摘要 | 哈播富碱侵入岩体位于云南省元阳县境内，该岩体位于红河-哀牢山富碱斑岩带南段西侧，近年来开始引起学者们的注意。目前，围绕着哈播富碱侵入岩体接触带及外围发现了一系列中小型铜、金及铅锌矿床。但是由于该地区相关矿床地质及地球化学研究较为薄弱，相关金矿床（哈播金矿、哈埂金矿、沙普金矿及舍俄金矿）-铅锌矿床（阿东铅锌矿及多脚铅锌矿）成因及这些矿床与区内哈播富碱侵入岩体的关系尚不清楚，这直接制约了该地区找矿勘探工作的进一步进行。本文通过系统研究区域地质背景、哈播富碱侵入岩体及相关金-铅锌矿床地质地球化学和年代学，探讨矿床成因，建立成矿模式，主要取得以下成果：1 岩体地质学及地球化学特征哈播富碱侵入岩体岩性主要为正长斑岩，具有较高K2O+Na2O, K2O＞Na2O，为高钾、富碱、过铝质类型，属钾玄岩系列。岩石富集大离子亲石元素，亏损高场强元素，显示出Ta、Nb和Ti具“TNT”负异常，显示出俯冲带幔源岩石的成分特点。哈播富碱侵入岩体不同单元岩石微量稀土元素特征基本一致，显示出不同岩石单元具有相似的岩浆来源和演化过程。2 岩体 U-Pb 年代学特征及构造环境LA-ICP-MS锆石U-Pb年代学研究表明，哈播富碱侵入岩体四个单元成岩年龄分别为：坪山单元（36.48±0.45Ma）；三道班单元（35.41±0.34Ma）；阿树单元（37.18±0.39Ma）；哈播南山单元（33.53±0.35Ma）。显示出哈播富碱侵入岩体形成于喜山期，与“三江地区”喜山期典型富碱斑岩形成峰期年龄一致。构造环境分析显示，哈播富碱侵入岩体主要形成于大陆弧环境。3 矿床元素及同位素地球化学特征a) 研究区金-铅锌矿床与哈播富碱侵入岩体有着相似的稀土元素配分图解，均为轻稀土富集的右倾配分模式，表明二者经历了相似的地球化学过程，具有相同的物质来源。b) 流体包裹体研究显示，金矿床成矿温度相对较高，分别为：哈播位于180℃~436℃之间（均值：309℃，n=18）、哈埂位于226℃~400℃之间（平均317℃，n=29）、沙普位于151℃~385℃之间（平均290℃，n=27）及舍俄位于183℃~324℃之间（平均258℃，n=23），而铅锌矿床成矿温度相对较低，分别为：多脚位于210℃~321℃之间（平均260℃，n=16））及阿东位于143℃~335℃（平均194℃，n=70）之间。所有矿床流体盐度总体位于10%附近，主要还是属于中等盐度流体，而包裹体温度随着矿床与哈播富碱侵入岩体空间关系的变化也显示出从金矿到铅锌矿依次递减的效应，这暗示金-铅锌矿床成矿流体属于同一流体。 c) 金-铅矿矿床硫同位素值位于-4‰～4‰之间。其中，哈播金矿、哈埂金矿和沙普金矿床硫同位素组成基本一致，集中在0值附近，其变化范围分别为-0.52~0.46‰（均值-0.05‰，n=6）、-0.21~2.69‰（均值1.13‰，n=6）和-1.91~-0.41‰（平均-0.98‰，n=5）；舍俄金矿硫同位素组成尽管有较大变化范围（-3.04~-0.05‰），但其均值（-1.42‰，n=5）也基本在0值附近；阿东和多脚铅锌矿硫同位素组成相对最低，以较小负值为特征，其变化范围分别为-3.82~-0.47‰（均值-2.72‰，n=7) 和-3.45~-3.37‰（均值-3.41‰，n=2），暗示金-铅锌矿床成矿物质主要为岩浆来源，而硫同位素值从金矿到铅锌矿的的递减效应则暗示二者具有相同物质来源，流体在搬运和矿质沉淀过程中硫同位素的分馏效应导致了递减效应的形成。d) 铅同位素研究表明，哈播富碱侵入岩体铅同位素组成相对均一，其206Pb/204Pb 变化范围为18.608~18.761，207Pb/204Pb 变化范围为 15.572~15.722，208Pb/204Pb 变化范围为 38.599~39.110。该岩体铅同位素组成特征与区内金矿床铅同位素组成非常相似，其206Pb/204Pb 变化范围为18.564~18.734，207Pb/204Pb 变化范围为 15.582~15.738，208Pb/204Pb 变化范围为38.592~39.319。而铅锌矿床的铅同位素组成和哈播富碱侵入岩体铅同位素组成有一定差异，但总体一致，其206Pb/204Pb 变化范围为 18.523~18.648，207Pb/204Pb 变化范围为 15.599~15.802，208Pb/204Pb 变化范围为 38.659~39.206。从哈播富碱侵入岩体与其周边金-铅锌矿床铅同位素组成来看，二者具有相似的铅来源，以地幔与下地壳混合的深源铅为主，仅一些矿床（特别是铅锌矿床）在成矿过程中上地壳物质的混入比例不同而导致其铅同位素组成上有一定差异。4 成矿年代学区内成岩成矿年代学对比研究表明，区内金矿床及铅锌矿床成矿时代属于喜山期，其成矿时代稍晚于哈播斑岩型铜-钼-金矿床。5 矿床成因通过对哈播富碱侵入岩体及其周边金-铅锌矿地质及地球化学研究认为，在喜山期，伴随着大规模的区域构造作用，诱发了富含铜、金、铅、锌等成矿物质的富碱岩浆的上侵，同时，从岩浆中分异出的含矿热液沿着构造断裂发育的马邓岩群变质地层运移，在有利的构造位置富集成矿。结合前人研究成果综合考虑，我们认为研究区金-铅锌矿床属典型斑岩型矿床，从哈播富碱侵入岩体中心到其周边围岩，其金-铅锌矿床大致展布格局为：哈播斑岩型铜-钼矿（岩体中心）-哈播、哈埂、沙普及舍俄金矿（岩体与围岩接触带）-阿东及多脚铅锌矿（远离岩体的围岩中）。 ; The Habo alkaline intrusion is a typical Cenozoic intrusion, located in Yuanyang county, Yunnan province, China, and is in southern of the Red river-Ailaoshan alkaline porphyry belt. There are a series of small to medium-sized Au and Pb-(Zn) deposits distributed around this intrusion. Those deposits are spatially associated with the Habo alkaline intrusion. However, studies of geology and geochemical about those deposits are very weak, genesis of Au ( Habo, Hageng, Shapu and Shee) and Pb-Zn (Adong and Duojiao) deposits and their relations with the Habo alkaline intrusion are not clear, which restricts further ore-prospecting work about this area. This paper will systematically study regional geology, geochemical and chronology of the Habo alkaline intrusion and its surrounding Au and Pb-Zn deposits, research the genesis of those deposits and their Metallogenic model. The main conclusions are listed as follows:1. Geology and geochemistry of the alkali-rich intrusionThe Habo alkaline intrusion, dominated by Syenite porphyry, has a characteristic of high K2O+Na2O and K2O＞Na2O, belongs to high K, alkali-rich and aluminum-rich type and shoshonite series. It enriched LILE and HFSE and show traits of TNT type negative anomaly of Ta, Nb and Ti, and reveals the characteristics of mantle source rock that derived from the subduction zone. Similarity of REE distribution patterns from the Habo alkaline intrusion four units (EP, ES, EA and EH) means they share the same source materials and evolution process.2. U-Pb chronology of zircons from the intrusion and its Tectonic backgroundU-Pb zircon dating of the four units of the Habo alkaline intrusion are 36.48±0.45Ma (EP), 35.41±0.34Ma (ES), 37.18±0.39Ma (EA) and 33.53±0.35Ma (EH), respectively. All ages belong to the himalayan period, which are consistent with the peak period of typical porphyries from the Sanjiang Area. Tectonic background study shows that the Habo alkaline intrusion belongs to continental arc type.3. Geochemistry characteristics of elements and isotopic compositionsa) Similarity of REE distribution patterns from the Habo alkaline intrusion and its surrounding Au and Pb-Zn deposits means both of them share the same source materials and evolution process.b) Fluid inclusions study shows that Au deposits have relative high ore-forming temperature with Habo ranging from 180℃ to 436℃(mean value: 309℃，n=18), Hageng from 226℃ to 400℃(mean value: 317℃，n=29), Shapu from 151℃ to 385℃(mean value: 290℃，n=27) and Shee from 183℃ to 324℃(mean value: 258℃，n=23). Pb-Zn deposits, however, have relative low ore-forming temperature with Duojiao from 210℃ to 321℃(mean value: 260℃，n=16) and Adong from 143℃ to 335℃(mean value: 194℃，n=70). Salinity of Au and Pb-Zn deposits are about 10%, means ore-forming fluids belongs to medium-salinity fluids. Otherwise, the descending effect of ore-forming temperature from Au to Pb-Zn deposits spatially means both of them share the same fluid.c) Sulfur isotopic data shows that almost all of the δ34S values ranging from -4.0‰ to 4.0‰: 1) the δ34S values of Au deposits range from-1.91‰ to 2.69‰ with Habo from (-0.52‰ to 0.46‰ (mean value = -0.05‰), Hageng from - 0.21‰ to 2.69‰ (mean value = 1.13‰), and Shapu from - 1.91‰ to 0.41‰ ( mean value = - 0.98‰). 2) the δ34S values of Pb-(Zn) deposit range from -3.82‰ to 0.05‰ with Shee from -3.04‰ to - 0.05‰ (mean value = - 1.42‰), Adong from - 3.82‰ to -0.47‰ ( mean value = - 2.72‰), and Duojiao from - 3.45‰ to - 3.37‰ (mean value = - 3.41‰), and both indicate that ore-forming elements mainly derived from magmatic fluids. Most importantly, the decreasing trend of δ34S mean values among those deposits may indicate that the Source of ore-forming elements of Au and Pb-(Zn) deposits derived from the Habo alkaline intrusion, the fractionation effects of sulfur isotopes may lead to the decreasing trend happened during hydrothermal migration and ore formation process.d) The Habo alkaline intrusion has relatively homogeneous Pb isotopic compositions within 206Pb/204Pb ranging from 18.608 to 18.761, 207Pb/204Pb from 15.572 to 15.722 and 208Pb/204Pb from 38.599 to 39.110, which are similar to those of Au deposits, whose 206Pb/204Pb ranging from 18.564 to 18.734, 207Pb/204Pb from 15.582 to 15.738 and 208Pb/204Pb from 38.592 to 39.319, both implying that Pb mainly derived from the depth, probably representing a mixture of mantle and crust. Pb-(Zn) deposits, however, show a decentralized trait, and most of them are similar to that of the alkaline intrusion within 206Pb/204Pb ranging from 18.523 to 18.648, 207Pb/204Pb from 15.599 to 15.802 and 208Pb/204Pb from 38.659 to 39.206. It can be concluded from the Pb isotopic compositions that all of deposits almost share the same source materials with the Habo alkaline intrusion, the source differences between some deposits, like Adong Pb deposit and Duojiao Pb deposit, and the Habo alkaline intrusion maybe are some sedimentary materials involved in during hydrothermal migrations and ore formation process.4. Metallogenic chronologyThe contrast study of rock and deposit chronology from the study area shows that the metallogenic age of Au and Pb-Zn deposits belongs to the himalayan period, their metallogenic age should be later than the Habo porphyry Cu-Mo-Au deposit.5. The genesis of Au and Pb-Zn depositsFrom systematically study regional geology, geochemical and chronology of the Habo alkaline intrusion and its surrounding Au and Pb-Zn deposits, it wise to conclude that a large regional tectonic action lead to the invasion of Cu-Au-Pb-Zn riched magma in the himalayan period, ore-forming fluids, meanwhile, flowed along with the faults that located in the Paleozoic Madeng rock group and enrichment. Combining with previous study results, we suggest that the Habo Au and Pb-(Zn) deposits typically are Ailaoshan-Red River Cenozoic alkaline-related deposits and ore-forming periods of these deposits are later than that of the Habo alkaline intrusion. Its metallogenic series including porphyry Cu-Mo, magma-related fracture hydrothermal vein type Fe-Au, and magma-related fracture hydrothermal vein type Pb-(Zn) deposits. |
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