Session 6 Li Chusi Evolution of Genetic Models for Magmatic Ni-Cu Sulfide Deposit 岩浆硫化物矿床成因

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些过 成程
Immiscible sulfide droplets segregated from the impact melt during due to super cooling settle into the embayment 小滴的不混溶硫化物在冲击熔融中分凝,在 特别冷的时候沉淀到港湾中
Early genetic model based on the Sudbury Ni-Cu deposits discovered
almost 2 centuries ago
基于两个世纪以前发现的萨德伯里铜镍硫化 物矿床所建立的早期成因模式
Canadian Pacific Railway near Murray
Acknowledgement: Some slides used in this presentation are from Tony Naldrett and Peter Lightfoot
致谢:本次讲解所用幻灯片部分由Tony Naldrett和Peter Lightfoot提供
世界级岩浆硫化物矿床
Evolution of Genetic Models for Magmatic Ni-Cu Sulfide Deposit
岩浆硫化物矿床成因模式的演化
Chusi Li
Indiana University China University of Geosciences-Beijing
李楚思
印地安那大学,中国地质大学(北京)
10% partial melting
(10%部分熔融)
@ N. Arndt
At ~10% melting, PGE, Au and Cu remain in sulfides; Ni is partitioned between sulfide and silicate phases; the melt is poor in Ni and PGE (10%熔融状态下,PGE、金和铜仍然在硫化物中;镍位于硫化物和硅酸 盐相之间;镍和PGE中的熔融很微弱)
r2 = 0.91, n = 159
S solubility limit
Causes of Sulfide Saturation
(饱和硫化物的形成原因) • Super cooling(过度冷却) • Fractional crystallization(分馏结晶) • Magma mixing(岩浆混合) • Assimilation of felsic crust(长英质地
1 mm
Crossed polars
Sulfide segregation due to super-cooling at Sudbury
在萨德伯里由于过冷造成的硫化物分凝
在硫化物饱和的岩浆中的硫含量
橄 榄 石 结 晶
分中亚 堆的层 积基是 并性局 保熔部 留体冲 在和击
岩高熔 体密融 边度产 角包物 及体 弯介并 曲入有 地对 带这流
(3) Fe-Ni-Cu-S phase relations(铁-镍铜-硫的相位关系)
(4) Ni, Cu, PGE partitioning(镍,铜, PGE分区)
Chusi Li
Indiana University, Bloomington China University of Geosciences, Beijing
ln XS = a + b(104/T) + c P + ΣdiXi
Coefficient (系数)
a b c d XSiO2 d XMgO d XFeO
Value (数值) 0.944 -0.579 -0.024 -5.58 -1.378 2.617
Std. Error (标准误差) 0.453 0.048 0.002 0.341 0.406 0.681
Controls on S solubility at sulfide saturation (硫在饱和硫化物中溶解度的控制因素)
Temperature(温度):
Positive(正相关)
FeO content( FeO含量): Positive(正相关)
Pressure(压力):
Negative(负相关)
经过几十年在大型层状侵入体中对萨德伯里型铜镍硫化物 矿床的探索,尽管没有成功,但最终我们意识到已经被萨 德伯里模式愚弄了很长时间。SIC是一个硫化物饱和的冲 击熔融岩席在过冷时形成的,不是在大陆岩浆作用过程中 的岩浆系统中发生的。
Genesis of Ni-Cu Sulfide Deposits Associated with Continental Magmatism
镍矿床
铂族矿床
Merensky Reef
镍矿产量+资源量(百万吨)
镍 的 品 位 用 百 分 比 表 示
铜-镍矿床
铂族元素矿床After Naldrett
Magmatic Associations of Ni-Cu deposits 1.Related to Komatiites (ultramafic lavas-principal example-
(2) Fluid or vapor transportation of S released from footwall(下盘释放出的硫 在流体和蒸汽中的运移)
How does mantle peridotite melt?
(地幔橄榄岩是怎样融化的)
@ N. Arndt
In peridotites, PGE, Cu and Au are mainly in small sulfide or alloy grains; Ni is partitioned between sulfide-alloy and olivine(橄榄岩 中,PGE,铜和金主要存在于小的硫化物或细粒合成硫化物中;镍被分 隔在合成硫化物和橄榄石之间)
基性岩浆的对流
亚层中的基性或超基性包体
下盘角砾岩
下盘角砾岩是部分熔融形成的冲击角砾岩,这些砾岩在上覆岩石冲 击熔融时,没有被改造而得以保留。
A Wake-up Call
一个突然的醒悟
After several decades of unsuccessful hunt for the Sudbury type Ni-Cu deposits in large layered intrusions, we finally come to realize that we have been fooled for too long by the Sudbury model. The SIC is a meteorite impact melt sheet in which sulfide saturation was induced by super-cooling that does not occur in magmatic systems of continental magmatism.
30% partial melting
(30%部分熔融)
@ N. Arndt
At ~30% melting, sulfide is completely resorbed; the melt becomes very rich in PGE+Au and moderately rich in Ni and Cu(在30%熔融状态下,硫 化物完全被再吸收;熔融物质含有大量的PGE和金,且含有较多的镍和铜)
含橄榄石变苏长岩包体的矿化的苏长岩亚层:Whistle矿山
Biotite-rich olivine melanorite with chrome spinel and 1.85 Ga zircon; Whistle Mine
含有铬尖晶石的富黑云母橄榄石变苏长岩和18.5亿年的锆石; Whistle矿山
Shocked Quartz from Onaping Formation
Onaping组中的冲击成因石英
Shatter Cones south of Kelley Lake
Kelley Lake南部冲击锥体
片麻岩 下盘角砾岩 亚层 浅色苏长岩 硫化物矿石
Mineralised Sublayer norite with olivine melanorite inclusion: Whistle Mine
Ni-Cu矿床岩浆组合 1.与科马提岩相关(主要为超基性熔岩,实例-Kambalda,Raglan) 2.与大陆溢流玄武岩相关(主要的实例-Noril’sk,以及Duluth,Insizwa) 3.与铁苦橄岩相关(主要的实例-Pechenga) 4.斜长岩侵入体组合(主要的实例-Voisey’s Bay) 5.橄榄岩-拉斑玄武岩岩浆(主要的实例为金川) 6.冲击熔融(仅有的实例-Sudbury)
Meteorite impact at Sudbury, ~1.85Ga
萨德伯里的陨石冲击,约18.5亿年
SUDBURY BRECCIA
萨德伯里角砾岩
Large vein of partial melt with blocks of granite gneiss
块状花岗质Fra Baidu bibliotek麻岩的部分熔融 形成的大脉体
非常重要的必备条件 (1)富铜和镍的岩浆 (2)在地壳水平时硫化物饱和 (3)在限定的地点的硫化物液体的浓缩
THEORIES(理论)
(1) Controls on S solubility at sulfide saturation(硫在饱和硫化物中溶解 度的控制因素)
(2) Genesis of fertile magma(富矿岩 浆的起源)
铜镍硫化物矿床的起源与大陆岩浆作用相关
Most Important Requisites (1) Ni-Cu fertile magma (2) Sulfide saturation at crustal levels (3) Concentration of sulfide liquids in limited localitie
壳的同化作用) • Addition of crustal S(地壳硫含量增
加)
Silicate/Sulfide Ratio
Addition of Crustal Sulfur
(地壳中硫含量的增加)
(1) Selective assimilation of S-bearing phases in country rocks(围岩中含硫相 的选择性同化作用)
This model suggests that magmatic Ni-Cu sulfide deposits occur in the base of large layered intrusions. It was regarded as an universal model in many textbooks and widely used in mineral exploration worldwide until recently. 这种模式提出了岩浆硫化物矿床产于大规模的侵入体中。在许多教科书中它已经被认为是个普 遍的模式,并且直到现今在矿产勘探中已被广泛的使用。
Kambalda,Raglan) 2.Related to Continental Flood Basalts (principal example-
Noril’sk, but also Duluth,Insizwa) 3.Related to Ferropicrites (principal example Pechenga) 4.Anorthosite plutonic suites (principal example-Voisey’s Bay) 5.Picrite-tholeiite magmas (principal example Jinchuan) 6.Impact melt (ONLY example-Sudbury)
Mine(Discovery Cut), photo taken Sept. 2,
1916 在Murray矿山附近的加拿大和平铁路(发现处 的露头),照片摄于1916年9月2日
The traditional view before 1980s
80年代以前的传统观点 侵入体 沉淀的硫化物
硫化物沿着侵入体基底低洼处聚积
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