长江中下游贵池矿集区燕山期岩浆作用与铜（钼）金成矿关系研究

发布时间：2018-04-23 07:03

  本文选题：年代学 + Sr-Nd-Hf同位素　； 参考：《中国科学技术大学》2017年博士论文

【摘要】：贵池地区金、银、铜、钼、硫等矿产资源丰富,系长江中下游成矿带七大铜金矿集区之一。区内晚中生代岩浆岩极为发育,并与本区铜金矿产有着密切的成因关联。晚中生代岩浆岩在该区分布广泛,该区晚中生代岩浆岩研究积累丰富,但是成岩与成矿之间的系统性关联仍有待进一步探讨。本文选择贵池地区铜山、安子山、老山、铜铃坡、宝树尖、铜山排铜矿和朱家冲、查册桥岩体金矿的含矿侵入岩和桂林郑花岗斑岩、杨山花岗岩为研究对象,开展详细的全岩地球化学、锆石年代学和原位Lu-Hf同位素、Sr-Nd同位素、矿物原位研究,示踪岩浆源区,探讨岩浆演化与成矿之间的关联,并为下一步矿产勘探提供指导性意见。锆石U-Pb年代学数据显示贵池地区晚中生代成矿相关岩浆活动分别集中于148-136Ma及130-125Ma早晚两个时期。早期成矿多为铜金矿床,晚期则以钼(铜)矿床(化)为主,具有与长江中下游地区其它矿集区相似的成矿特点。贵池地区第一阶段含矿侵入岩岩石系列为花岗闪长岩、闪长岩、二长花岗岩类,主要为高钾钙碱性系列,具有相对低的SiO2、高的Al2O3和MgO含量,强烈富集LREE和大离子亲石元素LILE,亏损HREE和高场强元素HFSE,具较强的Nb、Ta、Ti负异常,无明显Eu异常,大多数与俯冲洋壳型Adakite岩地球化学特征相近,起源于有限俯冲沉积物贡献的俯冲洋壳部分熔融,在上升过程中与富集地幔发生相互作用,并混染了古老地壳物质。贵池地区第二阶段岩浆岩岩石地球化学特征显示具有非常高的Si02,低的A1203,强烈的Eu负异常,富集Rb、Th、U、Nb、Ta等元素,强烈亏损Ba、Sr、P、Ti,具有典型的A型花岗岩特征,属于伸展构造体制下的产物。较年轻的 Nd 同位素模式年龄(1364～1490Ma),较高的 εNd(t)(-7.02～-5.47)、εHf(t)(7.5～5.9),说明岩浆来源于中-新元古地壳物质的部分熔融,并加入了新生地壳物质。在岩浆演化过程中存在斜长石、磷灰石、黑云母和Fe-Ti氧化物的结晶分异。通过锆石中稀土微量元素特征,得出早期埃达克(质)岩的锆石普遍具有较高的Ce4+/Ce3+值,反映了岩浆的高氧逸度;而晚期A型花岗岩的锆石的Ce4+/Ce3+值普遍偏低,指示了岩浆具有较低的氧逸度,与之对应的是早期的埃达克(质)岩更有利于铜金成矿。早期高氧逸度的岩浆岩形成于与俯冲有关的构造环境,而晚期的低氧逸度岩浆反映了构造体制的转换,这一构造环境的变化最可能是由俯冲板块后撤引发岩石圈伸展减薄所致。因此,贵池地区的岩石组合,即从早期的成矿埃达克(质)岩至晚期A型花岗岩,其形成可能与俯冲的古太平洋板块从下扬子岩石圈下后撤而引发的陆内岩浆过程有关。即古太平洋板块后撤,引发热的软流圈物质上涌,加热中新元古地壳物质并混合了新生地壳物质,从而导致了 了大量127Ma左右的A型花岗岩的形成。本区早期成矿作用与其岩浆活动相关,区内主要为岩浆期后热液成矿和接触交代成矿作用,矿化类型包括矽卡岩型、斑岩型、沉积叠改型及热液充填型等。晚期成岩成矿作用主要表现为由晚期岩浆侵入引起的中低温热液成矿作用和早期成矿基础上的叠加成矿作用。本区主逆冲断层以北属长江中下游成矿带主带,成矿主要与晚侏罗世中基性-中酸性高钾钙碱性岩浆侵入有关,与铜陵地区具相近的成矿作用和相近的矿体赋存规律;墩上-张溪断裂及其附近,成矿也主要与晚侏罗世中基性-中酸性高钾钙碱性岩浆侵入有关,同时也受到早白垩世酸性、碱性岩浆侵入的影响,两区成岩作用相近,且同受沿江构造-岩浆岩带控制。
[Abstract]:The Guichi area is rich in gold, silver, copper, molybdenum and sulfur. It is one of the seven major copper gold deposits in the middle and lower reaches of the Yangtze River. The late Mesozoic Magmatic Rocks in the region are extremely developed and closely related to the copper gold minerals in this area. Late Mesozoic Magmatic Rocks were widely distributed in this area, and the late Mesozoic Magmatic Rocks were rich in the area but formed in the area. The systematic association between rock and mineralization remains to be further discussed. In this paper, the Guichi area, Copper Mt., an Zi Shan, Laoshan, Tongling slope, Bao tree tip, Copper Mt. copper deposit and Zhu Jiachong, the ore bearing intrusive rock and Gui Linzheng granite porphyry and Yangshan granite in the jigqiao rock mass are selected as the research object, and the detailed whole geochemistry and zircon age are carried out in detail. The study and in situ Lu-Hf isotopes, Sr-Nd isotopes, mineral in situ studies, tracer magma source areas, explore the association between magma evolution and mineralization, and provide guidance for the next exploration of mineral exploration. The zircon U-Pb chronological data show that the late Mesozoic metallogenic related magma activities in the Guichi region were concentrated on two early and late 130-125Ma, 148-136Ma and 130-125Ma, respectively. The early mineralization was mostly copper gold deposits, and in the late stage the main mineralization was molybdenum (copper) deposit and similar to other ore deposits in the middle and lower reaches of the Yangtze River. The first stage of the Guichi area was granite diorite, diorite and two granitoid, mainly of high potassium calc alkaline series, with relatively low SiO2 and high level. The content of Al2O3 and MgO, strong enrichment of LREE and large ion stone element LILE, loss HREE and high field strong element HFSE, has strong Nb, Ta, Ti negative anomalies, and no obvious Eu anomalies, most of which are similar to those of subducted oceanic Adakite rocks. The subduction of subducted oceanic crust, which was derived from the contribution of the limited subduction sediments, was rich in the rising process. The second stage magmatic rock geochemical characteristics of the second stage magmatic rocks in Guichi region show that they have very high Si02, low A1203, strong negative Eu anomalies, enriched Rb, Th, U, Nb, Ta and so on, and have a strong loss of Ba, Sr, P, Ti, and are characteristic of typical granite type granites, which belong to the extensional tectonic system. The younger Nd isotopic age (1364 ~ 1490Ma), higher epsilon Nd (T) (-7.02 to -5.47) and epsilon Hf (T) (7.5 ~ 5.9) indicate that magma originated from partial melting of meso Neoproterozoic crustal materials and added to the new crustal substance. In the process of magma evolution, the crystallization of plagioclase, apatite, biotite and Fe-Ti oxide was different. The trace elements of the rare earth elements in the zircon show that the early age of the zircon of the early DAC (Qualitative) rock has a high Ce4+/Ce3+ value, reflecting the high oxygen fugacity of the magma, while the Ce4+/Ce3+ value of the zircons of the late A type granites is generally low, indicating that the magma has a lower oxygen fugacity. The early high oxygen fugacity of the magmatic rocks formed in the tectonic environment related to subduction, and the late low oxygen fugacity magma reflects the transformation of the tectonic system. This tectonic environment is most likely due to the extension and thinning of the lithosphere caused by the withdrawal of subducted plates. Therefore, the rock assemblage in the Guichi region is from the early metallogenic EDA. The formation of the late A type granites may be related to the intracontinental magma process caused by the subduction of the subducted paleo Pacific plate under the lower Yangtze lithosphere. That is, the paleo Pacific plate withdrew and the heating soft flow circle was upwelling, heating the Neoproterozoic crustal material and mixing the new crust material, resulting in a large amount of 127Ma. The formation of the left and right A type granites. The early mineralization in this area is related to its magmatic activity. The main areas are post magmatic hydrothermal mineralization and contact metasomatism. The mineralization types include skarn type, porphyry type, depositional superimposition and hydrothermal filling type. The late diagenesis and mineralization are mainly manifested in the middle stage of magma intrusion. The main thrust fault of the main thrust fault in this area is the main belt of the middle and lower Yangtze River metallogenic belt in the north of the region, and the mineralization is mainly related to the middle base intermediate acid high potassium calcium alkaline magma intrusion in the late Jurassic, which is similar to the Tongling area and the similar ore body occurrence law, and the pier Chang Zhang Xi fault. The mineralization is mainly related to the middle base intermediate acid high potassium calcium alkaline magma intrusion in the late Jurassic, and is also affected by the early Cretaceous acid and alkaline magma intrusion, and the diagenesis of the two region is similar, and is controlled by the tectonic magmatic belt along the river.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P618.2;P588.11
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本文编号：1790937