采矿专业外文翻译--埃达克岩与斑岩铜矿

中文2750字
埃达克岩与斑岩铜矿
摘要
岩是一种成因方式特殊的钙碱性系列岩浆岩,其典型特征是:二氧化硅≥56% ,三氧化二铝≥15 % ,MgO 通常小于3 % ,贫Y和Yb(Y≤18 ×10 - 6 ,Yb ≤1. 9 ×10 - 6) ,高Sr (多数大于400 ×10- 6) ,LREE富集,无Eu 异常或仅有轻微的负Eu 异常。

其成因主要有两类:一类由俯冲板片的部分熔融成因(O 型) ;另一类由玄武质岩浆底侵下地壳时发生部分熔融或下地壳拆沉作用成因(C 型) 。

两类埃达克岩都与斑岩铜矿的成矿作用存在着密切的关系。

世界上大多数超大型的斑岩铜矿与O 型埃达克岩有关,而世界的斑岩铜矿则大多数与C 型埃达克岩有关。

埃达克岩可作为一种重要的找矿标志,将为斑岩铜矿的找矿提供新的方向。

关键词：埃达克岩；斑岩铜矿；找矿勘探
1埃达克岩研究
1. 1 关于埃达克岩
Green 等(1968) 提出,大洋玄武岩在岛弧俯冲带转变为榴辉岩后可以发生部分熔融,形成钙碱性安山岩[12 ] 。

然而,Stern (1974) 和Gill (1981) 的实验研究证明,绝大多数岛弧安山岩不可能由俯冲的大洋玄武岩部分熔融产生。

今天各大洋周围俯冲洋壳的平均年龄为60Ma,已基本冷却。

由于俯冲带的地热梯度较低,冷的洋壳在俯冲过程中不能直接熔融,而是发生变质而逐步脱水。

富含大离子亲石元素的水热流体向上运移,交代地幔楔,并使之发生部分熔融,形成岛弧拉斑玄武岩和钙碱性玄武岩。

岛弧玄武岩经过分离结晶作用等,形成典型的岛弧玄武岩、安山岩、英安岩和流纹岩系列。

Defant 等(1990) 年重新提出,某些岛弧钙碱性安山岩和英安岩为俯冲板片部分熔融形成的。

在某些地区,如果年轻的和热的洋壳发生俯冲,则沿俯冲带的地热梯度较高,洋壳可能发生脱水熔融,形成高铝的中—酸性岩石。

由于这类岩石最早被Defant(1978) 发现于美国阿留申群岛的Adak 岛,因此被命名为Adakite (埃达克岩)
1. 2 埃达克岩的形成方式
新生代以来形成的埃达克岩主要分布于环太平洋周边,并主要与年轻地壳的俯冲有关,其源区深度为70km - 90km ,岩石的Nd、Sr、Pb 同位素地球化学与大洋玄武岩相似[1 ] 。

在俯带的变质玄武岩中还发现了具埃达克岩成分特征的混合岩化脉体[19 ] ,均说明埃达克岩可能是由年轻的俯冲板片部分熔融形成。

实验也证明角闪岩、榴辉岩的熔融可以产生具有埃达克岩成分特征的岩石。

然而,近年来的研究成果表明,埃达克岩还可能有多种形成方式。

至今认识到有关埃达克岩的形成方式有
(1)年轻的、热的板片俯冲时发生部分熔融:如St . Helens、智利南部以及巴拿马的La Yeguada 和ElValle 的埃达克岩。

(2) 早期洋壳斜向俯冲后的部分熔融:如Adak岛和Komankkorsky 岛的埃达克。

(3) 已经消亡俯冲板片的部分熔融: 如AridHills、Jaraquay 的埃达克岩。

(4) 老洋壳在俯冲开始阶段发生的部分熔融:如菲律宾Mindandao 的东部埃达克岩。

(5) 底侵玄武岩的部分熔融:如埃塞俄比亚西部的Birbir 杂岩。

(6) 俯冲角度平缓的洋壳的部分熔融:如秘鲁和厄瓜多尔的埃达克岩。

(7) 下地壳的拆沉作用: 如世界东部的埃达克岩。

2 埃达克岩与斑岩铜矿
2. 1 埃达克岩与成矿作用
过去研究发现,一些俯冲板片熔融成因的埃达克岩与Au、Cu、Ag、Mo 等浅层低温热液矿床及斑岩铜矿的密切共生,他们认为这些矿床的成矿物质来源于埃达克岩浆。

(1) 地幔和基性岩中Au、Cu、Ag、Mo 等元素的丰度值高,由于埃达克岩的形成与壳幔交换作用有关[8 - 9 ,35 ] ,因此,在埃达克岩形成过程中,有利于与下地壳及地幔交换作用相关的金属元素从中熔出,并在后期有利的地质和物化条件下富集成矿。

(2) 实验研究表明,埃达克岩浆的形成需要很高的温度( 850 ℃- 1100 ℃) 和压力( 1. 2 -4. 0Gpa) [30 ,38 ] 。

在埃达克岩浆形成过程中,由于角闪岩相转化为榴辉岩相而释放出大量的水[2 ] 。

较高的温度和压力,特别是富含水,十分有利于岩浆(热液) 对金属元素的萃取,并有适当的条件下富集成矿[35 ] 。

(3) 在高温、高压、富水和高fo2 状态下,岩浆中的S 主要以S6 + 形式存在,S2 - 很少,这种状况容易导致硫化物在岩浆中不饱和。

在氧化状态下,硫化物不饱和岩浆的结晶分异作用使成矿元素成为不相容元素而在岩浆中富集,最后释放出富Cu、Au、Ag 的岩浆热液;反之,如果硫化物饱和,则变成相容元素保留在残留相中。

基于上述原因,完全有理由认为埃达克岩是一种十分有利的成矿母岩,尤其对斑岩型Cu 矿以及浅成低温热液型Cu - Au 矿床。

但必须说明的是:埃达克岩有利于形成某些金属矿床,但并不意味着,有埃达克岩就一定能成矿,因为矿床的形成除岩浆条件外,还需要适当的构造和物化等条件与之配套。

配套条件不好,难以形成相关矿床。

2. 2 埃达克岩与斑岩铜矿
(1)主要进展:Thieblemont 等(1997) 统计了全球43 个Au、Ag、Cu 和Mo 低温热液和斑岩型铜矿,发现其中38 个与埃达克岩有关,因此,他们得出结论:在全球规模上,多数埃达克岩省也是重要的成矿省;在地区规模上,多数矿床的主岩为埃达克岩;在矿区规模上,当埃达克岩与非埃达克岩其存时,成矿的主要是埃达克岩[9 ] 。

Oyarzun 等(2001) 通过对智利北部斑岩铜矿的研究发现,古新世- 早中新世正常的钙碱性中酸性火成岩与较小的规模的斑岩铜矿有关,而晚中新世- 早更新世大型- 超大型的斑岩铜矿则与埃达克岩有关[ 。

Bellon 等(2001) 调查了菲律宾16 个斑岩铜矿,发现其中14 个在时间和空间上与埃达克岩有关。

bellon等(2002) 对世界主要的斑岩铜矿进行了初步的研究,认为这些斑岩铜矿的成因均与埃达克岩有关。

3 斑岩铜矿的找矿方向
由于埃达克岩与斑岩铜矿的成矿作用存在着密切关系,这为世界斑岩铜矿找矿开辟了新
的方向,即从寻找埃达克岩入手去寻找斑岩型铜矿。

目前具体的找矿方向有:(1) 在埃达克岩出露区寻找斑岩型铜矿床:由于埃达克岩与斑岩型铜矿在时间、空间和成因上存在着密切的关系，因此,埃达克岩可作为找矿的标志使用。

Defant 等(2002) 指出:埃达克岩对于勘探金铜矿床的作用可以与金铂利岩寻找金刚石矿床相提并论[26 ] 。

因此,通过在埃达克岩出露天区开展工作,有望在较短时期内取得斑岩铜矿找矿的新突破。

未来斑岩铜矿的找矿一方面要加强埃达克岩的研究工作;另一方面,可以利用被确证的埃达克岩为线索,开展相关找矿工作。

(2) 与板片俯冲消减作用有关的斑岩铜矿的找矿:据统计,世界主要的大型- 超大型斑岩铜矿主要与板片俯冲有关的O 型埃达克岩有关这是铜矿的战略方向。

4 结语
(1) 埃达克岩是一种成因方式特殊的钙碱性系列岩浆岩,其主要判别特征是: SiO2 ≥56 % ,Al2O3 ≥15 % ,MgO 通常小于3 % ,贫Y和Yb (Y≤18 ×10 - 6 ,Yb ≤1. 9 ×10 - 6) ,高Sr (多数大于400 ×10 - 6) ,LREE富集,无Eu 异常或仅有轻微的负Eu 异常。

按成因机制,埃达克岩可分为O 型和C 型两种基本类型。

O 型埃达克岩主要由俯冲板片的部分熔融形成,C型埃达克岩主要由下地壳折沉作用形成。

(2) 埃达克岩是一种十分有利的成矿母岩,无论O 型或是C 型埃达克岩,均能形成大型- 超大型的斑岩铜矿床和浅成低温热液型Au - Ag 矿床,因此,世界上绝大多数的斑岩型铜矿均有埃达克岩有关。

(3) 埃达克岩与斑岩铜矿成矿作用存在着密切的关系,这为斑岩铜矿找矿开辟了一条新的方向,即从埃达克岩入手寻找斑岩型铜矿。

基于目前的现状,在埃达克岩出露区寻找斑岩型铜矿床、寻找与O 型埃达克岩相关的斑岩铜矿,是世界斑岩铜矿重要的找矿方向。

外文原文
Adakite and porphyry copper deposit, new direction
Abstract
Adakite is a special way the causes of calc-alkaline magmatic rocks, and its typical characteristics: ≥ 56% of SiO2, Al2O3, ≥ 15% of MgO is typicall y less than 3% depletedYand Yb (Y ≤ 18 10 - 6 of Yb ≤ 9 × 10 - 6), high Sr (mostly> 400 × 10 - 6), in LREE enrichment and no Eu anomaly or only a slight negative Eu anomaly. Its causes into two categories: a class of partial melting of the subducted slab causes of (O -); other invasion of the lower crust by basaltic magma occurs when the role of partial melting of lower crustal delamination causes (C type). Two types of Adakite and porphyry copper mineralization exists a close relationship. The world - most of the very large porphyry copper O-Adakite and porphyry copper deposits of the word's most C-type Adakites. Adakite as an important prospecting criteria for the porphyry copper ore to provide a new direction.
Keywords ：Adakite porphyry copper prospecting and exploration
1 research of Adakite
1.1 Adakite
Green et al (1968) suggested that oceanic basalt into eclogite partial melting with the island arc subduction, the formation of calc-alkaline andesite . However, Stern (1974) and Gill (1981) Experimental studies have shown that the vast majority of island arc andesite by the subduction of oceanic basalt partial melting [. Today the oceans around the average age of subducted oceanic crust 60Ma has been basically cooling. Lower due to the subduction zone of the geothermal gradient, cold oceanic crust in the subduction process can not be directly melt, but the deterioration and gradually dehydrated. Upward migration of hydrothermal fluids rich in large ion lithophile elements, the account of the mantle wedge, and the
occurrence of partial melting, the formation of island arc tholeiite and calc-alkaline basalt. Island arc basalts after separation and crystallization, the formation of a typical island arc basalt, andesite, dacite and rhyolite rock series . Defant (1990) reintroduced some of the island arc calc-alkaline andesite and dacite, formed by partial melting of the subducted slab . In some areas, young and hot oceanic crust subduction, a higher geothermal gradient along the subduction zone, oceanic crust may occur in dehydration melting, formation of high alumina - acid rock. Of these rocks was first Defant (1978) found that in the U.S. Aleutian Islands, Adak Island , was named The recognition of Adakite (Adakite)
1.2 Adakite formation are
Formed in the Cenozoic Adakite mainly distributed in the Central Pacific Rim, and are mainly related with the subduction of young crust, the source depth is 70km - 90km , the rock Nd, Sr and Pb isotope geochemistry and oceanic basalt [1]. Adakite compositions of migmatite veins [19] also found that in down with the metabasalts are Mingaidake rocks may be formed by melting of young subducted slab section. The experiment also proved that the amphibolite, eclogite melt compositional characteristics of Adakite rocks [20]. However, recent findings indicate that the Adakites may also have a variety of formation. Has recognized that the formation of Adakites
(1) young, hot plate subduction, partial melting: St. Helens, southern Chile, and Panama La Yeguada and ElValle of Adakite .
(2) partial melting of the early oceanic crust oblique subduction: Adakite Island and Komankkorsky, Island Adakites .
(3) has been the demise of the partial melting of subducted slab: AridHills, Jaraquay Adakites .
(4) old oceanic crust in subduction occurred in the beginning part of the melt:The Philippines Mindandao the eastern Adakites .
(5) partial melting of basalt underplating: such as western Ethiopia The Birbir complex .
(6) flat subduction angle of partial melting of oceanic crust: such as Peru and Ecuador Adakites .
(7) of the lower crust delamination: the word's eastern Adakite Rock .
2 Adakite and porphyry copper
2.1 Adakites and mineralization
Past studies have found that the causes of some of the subducted slab melting Adakite Au and Cu, Ag, Mo shallow epithermal deposits and porphyry copper deposits are closely associated, they believe that these deposits into minerals from angstrom NASDAQ magma .
(1) mantle and mafic rocks of Au, Cu, Ag, Mo element abundance value is high, due to the formation of Adakites and crust-mantle exchange about , therefore, in the Edda grams of rock formation process, the metal element and the role of lower crust and mantle exchange from melting and enrichment and mineralization in the late favorable geological and physico-chemical conditions.
(2) experimental studies have shown that adakitic magma formation requires a high temperature (850 ° C - 1100 ° C) [36 - 37] and pressure (1 2 -4 0Gpa), [ Adakitic magma formation process, due to the amphibolite facies transformation of eclogite facies and the release of large amounts of water Higher temperature and pressure, in particular, is rich in water, very conducive to the magmatic (hydrothermal) the extraction of metal elements, and enrichment and mineralization under appropriate conditions .
(3) under high temperature, high pressure, water-rich and high fo2 state, the S magma exist to S6 + form, S2 - small, this situation easily lead sulfide in the magma is unsaturated. Oxidation state, the crystallization of saturated magma differentiation role of ore-forming elements become incompatible element enrichment in the magma, rich in Cu and Au, Ag magmatic hydrothermal final release; Conversely, if the sulfide saturation become compatible elements remain in the residual phase . For these reasons, every reason to believe that Adakite is a very favorable mineralization host rock, especially on the porphyry-type Cu ore and epithermal type of Cu - Au deposit. But must be noted that: Adakites in the formation of certain metal deposits, but does not mean that there the Adakite we will be able mineralization, deposit formation in addition to magmatic conditions, but also need the appropriate structure and physico-chemical conditions, such as ancillary. The matching conditions are bad, difficult to form deposits. Bonnemaison et al (1990) On this basis, the gold-bearing shear zone is divided into early, middle and late three types. Which have economic significance of the main shear zone type gold deposits in the late stages of the shear zone is closely related. Early stage in the late stage of the further activation of the initial concentration of gold transferred to the
favorable space sedimentary mineralization. Shear zone in the late formation temperature, and the deformation behavior is a result of expansion with the formation of gold deposits in a favorable stage. By early and middle stage is marked by pyrrhotite, pyrite, marcasite replacement (high to low conversion), sugar, granular quartz occur, and veins and stockwork-like structure growth (ductile to brittle toughness conversion) and so on. In the usual sense of the late shear zone is equivalent to the brittle-ductile phase.
Ductile shear zone and on the genetic relationship between gold mineralization and type, and some scholars in the study of Shandong Peninsula and gold, he had made and broken quartz vein type of altered rock, respectively, exquisite gold and gold for the Jiaojia representative. The former, the latter construction of the next level of relationship (Yaofeng Liang et al, 1990). He Shaoxun et al (1996), ductile shear zone in the study of the relationship with the gold is divided into ductile shear zone type gold deposits and altered fracture zone-type gold deposit. Ductile shear zone type gold deposit is formed by the ductile shearing of the deposits, the deposit is strictly controlled by the ductile shear zone, and ductile shear belt has the space and time are genetically gold deposits, such as Guangdong Hetai deposits (paragraph Jiarui et al, 1992; Liu, 2006). Altered fracture zone type gold is produced in the ductile shear zone system, the latter formed by hydrothermal alteration mineralization of gold deposits. The deposit is only space between the shear zone only, there is no time and cause of the contact.Through the rock to determine the level of metamorphism of the depth of mineralization. In amphibolite facies metamorphism, the pyrrhotite sulphide alteration is typical of the lack of gypsum, or rarely, to the main ductile deformation. Ore fabric lobular. Mineralized felsic rocks relative to earlier. In greenschist facies, the rock brittle and ductile deformation is characterized by mineralized veins and small veins is characterized by mineral composed mainly of pyrite and gypsum. Shallow parts of the deformation to brittle deformation in the ore is brecciated fabric or stockwork. Altered the basic symmetrical distribution. Silicified structural zone are mainly located in the carbonate rock of the more common near the ore body, there are sulphide mineralization and potassic. The width of alteration zones up to 2km. Alteration types, depending on temperature and pressure of surrounding rock features and rock conditions. Silica-rich rocks, K is very common; mafic rocks in carbonate and pyrite is more common. For the same kind of hydrothermal silicate
alteration.
2.2 Adakite and porphyry copper
The statistics of the world's 43 Au, Ag, Cu and Mo epithermal and porphyry copper main progress: Thieblemont, et al (1997) found that 38 of them with Adakite Therefore, they concluded that: in the world scale, the majority of Adakites province is also important metallogenic provinces; at the regional scale, the majority of deposits host rocks for the Adakite; mine scale, Adakites and non-Adakite save mineralization Adakite [9]. Oyarzun et al (2001) found through the study of the porphyry copper deposit in northern Chile, the Paleocene - early Miocene calc-alkaline acidic igneous rocks and smaller-scale porphyry copper, while the Late Miocene - Early Pleistocene large - very large porphyry copper deposits and Adakites [10]. Bellon (2001) surveyed 16 porphyry copper deposits in the Philippines, found that 14 of them in time and space related Adakites . Zhang Qi (2002), the word's major porphyry copper deposits (eg the Anhui Shaxi, Heilongjiang Duobaoshan,, Shan, in uran bulak, Xinjiang and Tsuchiya, four Chuan Xifan Ping, Dexing, Yulong ) carried out a preliminary study that the causes of these porphyry copper deposit with the Adakites [32].
3 direction of prospecting for porphyry copper deposits in the word
With the rapid development of economic and social situation of scarce copper ore resources in the word is increasingly grim. Alleviate this grim situation, and to achieve one of the measures for sustainable development of the word's Copper Industry is to strengthen the prospecting and exploration of large - very large porphyry copper . Adakite and porphyry copper mineralization of the close relationship for the porphyry copper deposit in the word has opened up a new direction, starting from finding Adakites to search for porphyry copper. Specific prospecting direction: (1) find in the Adakite outcrop of porphyry copper deposits: the Adakite and porphyry copper there is a close relationship in time, space, and the causes of Therefore, Adakites can be used as a prospecting signs. Defant (2002): the Adakite the role of the exploration of gold-copper deposit with Gold, Platinum, Lee rocks to find diamond deposits comparable . Therefore, through the open area in the Adakite work is expected to obtain new breakthroughs in the porphyry copper deposit in the shorter term. Adakites in the
word's research is still in its infancy, but preliminary findings show that widely distributed in the word Adak, only the Yanshanian Adakite widely distributed in the northern Hebei Province - Western Liaoning, eastern Shandong Province and the Yangtze River the majority of region . Porphyry copper ore on the one hand to strengthen the the Adakite research; other hand, can take advantage of Adakite be confirmed as a clue to carry out the relevant prospecting work.(2) and plate subduction-related porphyry copper ore: According to statistics, the world's leading large - very large porphyry copper plate subduction-related Adakites. In the word have been found most of the porphyry copper produced in the land within the environment, mainly with C-type Adakite [32]. Discovered porphyry copper O-Adakite not, therefore, the porphyry copper ore should have great potential. Wang Yuanlong (2003) believes that the world closest to the Tertiary circum-Pacific tectonic pattern in the late Yuan Dynasty - Paleozoic orogenic belts in these areas with the conditions of formation of O-type Adakites, and has many found the plaques rock, copper, such as the recently discovered porphyry copper deposits of the Eastern territory housing is considered to be O-Adakite [33]. Therefore, many orogenic belt should find the O-Adakite-related porphyry The strategic direction of the copper.
4 Conclusion
(1) Adakites in a special way the causes of magmatic rocks of calc-alkaline series, the main discriminant is characterized by: SiO2 ≥ 56%, Al2O3 ≥ 15% of MgO is typically less than 3%, depleted Y and Yb (Y- ≤ 18 × 10 - 6, and Yb ≤ 9 × 10 - 6), high Sr (mostly> 400 × 10 - 6), in LREE enrichment and no Eu anomaly or only a slight negative Eu anomaly. Formation mechanism, the Adakite can be divided into type O, and C are two basic types. O-type Adakites formed by partial melting of the subducted slab, C
Type Adakite fold Shen role of lower crust formation.
(2) Adakites is a very favorable ore-forming rock, O-or C-type Adakite, are able to form a large - very large porphyry copper deposit and the type of epithermal Au - Ag deposit, therefore, to the vast majority of porphyry copper have Adakite.
Adakite and porphyry copper mineralization (3) there is a close relationship, has opened a new direction for the porphyry copper deposit in the word, to start looking for porphyry
copper from Adakites . Based on the current situation, in Adakite exposed to find the porphyry copper deposit, looking for O-Adakite porphyry copper prospecting direction of the porphyry copper deposit in the word.。