新疆东天山地区白鑫滩与路北铜镍硫化物矿床成因研究

发布时间：2018-05-06 17:58

本文选题：含铜镍矿镁铁-超镁铁岩体 + 侵入期次　；参考：《合肥工业大学》2017年硕士论文

【摘要】：自上世纪70年代以来,新疆东天山地区库姆塔格沙垅以东地区发现了大量的镁铁-超镁铁岩体和岩浆铜镍硫化物矿床,但是在沙垅以西地区没有大的找矿突破。白鑫滩及路北含铜镍矿镁铁-超镁铁岩体为近几年在库姆塔格沙垅以西地区发现的岩浆铜镍硫化物矿床,研究工作薄弱,本文通过对白鑫滩及路北含铜镍矿镁铁-超镁铁岩体的岩石学、年代学、岩石地球化学、S同位素、Sr-Nd同位素和O-Hf同位素分析来解释其岩石及矿床成因。白鑫滩岩体不同岩相中矿物的粒径和含量的变化规律说明岩体为三期岩浆侵入作用形成,第一期为顶部的角闪辉长岩;第二期的橄榄辉长岩、斜长二辉橄榄岩和含长橄榄二辉岩,矿物种类相同,含量呈渐变关系;岩体底部为第三期侵入的角闪辉长岩,矿物粒径相对顶部的角闪辉长岩较小。白鑫滩岩体与黄山东、黄山西岩体具有相似的稀土元素和微量元素配分型式,大离子亲石元素(Rb、Ba、U、K)相对富集,而部分高场强元素(Nb、Ta、Ti)相对亏损,稀土元素呈轻稀土略微富集的右倾样式,均表现出岛弧火山岩的地球化学性质,εNd(t)值(2.84~5.05)和(87Sr/86Sr)(t)值(0.704113~0.705682)介于软流圈地幔与岩石圈地幔之间。但是与黄山东、黄山西岩体相比,白鑫滩岩体不相容元素含量更高,且εNd(t)值更低,(87Sr/86Sr)(t)值更高,还具有较高的La/Nb(2.00~3.33),较低的La/Ba(0.02~0.15),这些特征说明白鑫滩岩体的原始岩浆为岩石圈与软流圈物质相互作用的产物,且白鑫滩岩体的原始岩浆中软流圈物质相对于黄山东和黄山西岩体加入的比例更小。路北岩体不同岩相矿物含量的变化规律、锆石U-Pb定年结果说明岩体为两期岩浆侵入作用形成,第一期为斜长二辉橄榄岩和橄榄辉石岩;第二期为辉长岩。路北岩体与黄山东、黄山西岩体具有相似的稀土元素和微量元素配分型式,微量与稀土元素总量略高于黄山东,与黄山西基本一致,表现为大离子亲石元素(Rb、Ba、U、Sr)相对富集,而部分高场强元素(Nb、Ta、Ti)相对亏损。这些特征说明路北岩体与黄山东、黄山西岩体相同,母岩浆都可能来自于受俯冲流体交代地幔的部分熔融。白鑫滩橄榄辉长岩年龄为287±3Ma,路北辉长岩年龄为277.8±3.4Ma,晚于该地区蛇绿岩(336-503Ma)、岛弧火山岩(320~322Ma)、岛弧花岗岩(316~328Ma)和含矿斑岩侵入体(326~334Ma)的年龄,与A型花岗岩和双峰式火山岩(284~294Ma)的年龄基本一致,而且白鑫滩与路北岩体单斜辉石的化学成分与拉张裂谷环境的堆晶岩相似,因此推断白鑫滩与路北岩体形成于后碰撞拉张环境。岩浆岩及同位素特征显示橄榄石等矿物的结晶分异作用可能是促使白鑫滩和路北岩浆中硫达到饱和的因素,也可能存在岩浆同化混染地壳围岩而使硫化物达到饱和并促使硫化物发生熔离。在后碰撞拉张环境下,东天山地区经历了岩石圈加厚拆沉,软流圈地幔物质上涌,岩石圈地幔物质发生部分熔融,从而形成玄武质岩浆。这些玄武质岩浆断裂上侵,橄榄石等矿物发生结晶分异,从而形成白鑫滩及路北镁铁-超镁铁质岩体,同时由于地壳物质混染的影响,硫化物发生饱和并产生熔离作用,硫化物珠滴被不断上涌的岩浆带人到岩浆平缓处,聚集沉降成矿体,即形成了白鑫滩和路北铜镍硫化物矿床。
[Abstract]:Since the 70s of last century, a large number of mafic ultramafic and magmatic copper nickel sulfide deposits have been found in the eastern Tianshan area, east of Xinjiang, but there are no major breakthroughs in the west of the sand ridge. The white and lukinites, the copper nickel ore, the magnesium iron and the ultramafic rocks are in the west of Kum Tagg Shah Rang in recent years. The discovery of magma copper nickel sulfide deposit is weak. In this paper, the lithology, chronology, geochemistry, S isotopes, Sr-Nd isotopes and O-Hf isotopes of the mafic and ultramafic rocks in Bai Xin Tan and Lubei bearing copper nickel ore are analyzed to explain their rock and ore deposits. The variation of the quantity shows that the rock mass is formed by the three phase of magma intrusion, the first stage is the hornblende gabbro on the top, the second olivine gabbro, the long two glow peridotite and the olivine two pyroxenite, the mineral species are the same, the content shows a gradual change, and the bottom of the rock mass is a third phase of the amphibolite, the mineral particle size relative to the top of the hornblinde. The gabbro is smaller. The Bai Xin beach rock mass is similar to the Yellow Shandong and Mount Huangshan Western rocks with a similar distribution pattern of rare earth elements and trace elements, and the large ionic stone elements (Rb, Ba, U, K) are relatively rich, while some of the high field and strong elements (Nb, Ta, Ti) are relatively deficient, and the rare earth elements are slightly enriched in light dilute soil, showing the geochemistry of the island arc fire rocks. The Nd (T) value (2.84~5.05) and (87Sr/86Sr) (T) value (0.704113~0.705682) are between the asthenosphere mantle and the lithosphere mantle. But compared with the Yellow Shandong and Mount Huangshan Western rocks, the white Xin beach rock mass has higher content of incompatible elements, lower Nd (T), (87Sr/86Sr) (T) higher, and higher La/Nb (2.00~3.33). 0.15) these characteristics indicate that the original magma of the Bai Xin Tan rock mass is the product of the interaction of the lithosphere and the asthenosphere, and the proportion of the soft fluid in the original magma of the Bai Xin Tan rock mass is smaller than that of the Yellow Shandong and the western Mount Huangshan rock mass. The variation of the mineral content of the different lithofacies in the Lubei rock mass, and the zircon U-Pb dating results to illustrate the rock The body is formed by two phases of magma intrusion, the first phase is the long two glow peridotite and olivine pyroxenite, and the second phase is gabbro. The Lubei rock mass is similar to the Yellow Shandong and Mount Huangshan Western rocks with rare earth elements and trace elements. The amount of trace and rare earth elements is slightly higher than that of the Yellow Shandong, which is basically consistent with the western Mount Huangshan, showing the large ionic affinity. Shi Yuansu (Rb, Ba, U, Sr) is relatively rich, while some of the high field and strong elements (Nb, Ta, Ti) are relatively deficient. These characteristics indicate that the Lubei rock mass is the same as the Yellow Shandong and Mount Huangshan West Rock, and the parent magma may come from partial melting of the subducted fluid metasomatism. The age of the white Xin beach olivine gabbro is 287 + 3Ma, and the age of the luperyte gabbro is 277.8 + 3.4Ma. The age of the ophiolite (336-503Ma), island arc volcanic rock (320~322Ma), island arc granite (316~328Ma) and ore bearing porphyry intrusion (326~334Ma) is basically the same as the age of A type granite and Shuangfeng type volcanic rock (284~294Ma), and the chemical composition of the clinopyroxene in Bai Xin Tan and Lubei rock mass is similar to that of the rift valley. Therefore, it is inferred that the white Xin beach and the Lubei rock mass are formed in the post collision tension environment. The magmatic and isotopic characteristics show that the crystallization differentiation of the olivine and other minerals may be the factors contributing to the saturation of sulfur in the magma of Bai Xin beach and Lubei magma, and may also exist in the magma assimilation of the surrounding rock of the crust to saturate the sulfide and promote the sulfide hair. In the post collision and stretching environment, the East Tianshan region experienced the lithosphere thickening and subsidence, the soft flow mantle material upwelling and the partial melting of the lithosphere mantle material, resulting in the formation of basaltic magma. These basaltic magmas were invaded and the minerals such as olivine were crystallized and differentiated, thus forming white Xin Beach and luthinite ultramafic iron. The pluton, at the same time, is saturated and melted by the contamination of the crustal material, and the droplets of the sulfide beads are continuously upwelling to the gentle place of the magma, and accumulate and settle into the orebodies, that is, the Bai Xin beach and Lubei copper nickel sulfide deposits have been formed.

【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.41;P618.63

【参考文献】