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花岗斑岩侵入玄武岩中形成相应的铜钼矿化是三江成矿带的特色之一,三江南段的澜沧老厂多金属矿床的花岗斑岩隐伏侵入石炭系玄武质火山岩中,花岗斑岩-玄武岩热液蚀变体系得以完整保存。在确立初始岩石端元的基础上,对花岗斑岩顶盖相的去钠化蚀变及玄武质围岩夕卡岩化过程的元素地球化学进行了初步研究,主要结论包括:(1)花岗斑岩驱动的热液体系以富含Na-Ca-Si-Mn为特征,Na-Ca-Si主要来自花岗斑岩中的斜长石分解蚀变,在花岗斑岩顶盖相中形成极度的Na亏损和极高的K_2O/Na_2O比值(去钠化蚀变);Si在花岗斑岩顶盖相中弱富集,Si-Ca在玄武质围岩夕卡岩化过程中明显富集(w(Si O_2)平均增加了4%~5%,w(Ca O)平均增加了5%左右),目前在蚀变体系中没有发现Na的明显富集,推测Na可能被热液搬运进入地表径流系统;Mn是特征蚀变元素,可能来自深部花岗斑岩,在花岗斑岩顶盖相及玄武质围岩中都得到明显富集(平均富集0.4~1.2倍)。(2)矿化元素中Mo主要来自花岗斑岩,在斑岩顶部及玄武质围岩中富集,局部成矿;Sn-Zn主要来自花岗斑岩,但目前没有在花岗斑岩内外接触带发现矿化;Ag-Pb-Bi的主要物源是玄武岩,在斑岩顶部富集,在更远端的碳酸盐岩地层中成矿;Cu也主要来自玄武岩,在玄武岩夕卡岩化过程中局部成矿。(3)稀土元素在花岗斑岩的蚀变过程主要表现为活化迁移亏损,在活化过程中Eu发生了比较明显的分异(δEu 0.85~1.32);玄武岩夕卡岩化过程中,热液流体携带的稀土元素在橄榄玄武岩中基本收支平衡,但在拉斑玄武岩中明显富集,并以显示弱的正Eu异常为特征。
Granite porphyry invaded the basalts to form the corresponding copper and molybdenum mineralization is one of the characteristics of the Sanjiang metallogenic belt. The granite porphyry of the Lancang Laohang polymetallic deposit in the southern part of Sanjiang area invaded the Carboniferous basaltic volcanic rocks, Granite porphyry - basaltic hydrothermal alteration system to be completely preserved. On the basis of establishing the initial rock end-element, the de-sodiumification alteration of the granite porphyry caprock facies and elemental geochemistry of the basaltic skarn kyanification process are preliminarily studied. The main conclusions are as follows: (1) The hydrothermal system driven by granite porphyry is characterized by Na-Ca-Si-Mn enrichment. The Na-Ca-Si mainly comes from the plagioclase alteration alteration in granite porphyry. (Na-depleted alteration); Si is weakly enriched in the granite porphyry caprock facies, and Si-Ca in the skarnization of basaltic rocks Significant enrichment (W (Si O 2) increased by 4% ~ 5% on average and w (CaO) increased by about 5% on average), no obvious enrichment of Na was found in the alteration system at present, Liquid transported into the surface runoff system; Mn is a characteristic alteration element possibly from deep granite porphyry, which is obviously enriched in granite porphyry caprock facies and basaltic rocks (average enrichment 0.4-1.2 times) . (2) Mo in the mineralized elements is mainly from granite porphyry, which is enriched in the top of porphyry and basaltic rock and locally mineralized. Sn-Zn mainly comes from granite porphyry, but there is no granite porphyry The main source of Ag-Pb-Bi is basalt, enriched at the top of the porphyry and mineralization in more distant carbonate formations; Cu is also mainly derived from basalts, Local mineralization in the process of petrification. (3) The alteration process of rare earth elements in granite porphyry mainly shows the loss of activation and migration. During the activation process, Eu has a relatively obvious differentiation (δEu 0.85 ~ 1.32). During the basalt skarnization, The fluid-borne rare earth elements have a basic balance of payments in olive basalts, but are significantly enriched in tholeiitic basalts and are characterized by a weak positive Eu anomaly.