西南天山阔克萨彦岭地区巴雷公地幔橄榄岩成因及其地质意义

王超; 刘良; 罗金海; 车自成; 张静艺; 桂小军

西南天山阔克萨彦岭地区巴雷公地幔橄榄岩成因及其地质意义

王超^{1, 2,},
刘良²,
罗金海²,
车自成²,
张静艺²,
桂小军³

1.
中国地质调查局西安地调中心, 陕西西安 710054
2.
大陆动力学国家重点实验室, 西北大学地质学系, 陕西西安 710069
3.
长庆油田公司勘探开发研究院, 陕西西安 710021

基金项目:

国家自然科学基金项目 Nos40372088

国家自然科学基金项目 40572111

国家自然科学基金项目 40472043

中国地质调查局国土资源大调查研究项目 No1212010510416

详细信息

作者简介:
王超(1979-), 男, 博士生, 岩石大地构造学专业.E-mail: wangc-mail@163.com

中图分类号: P588.14;P59;P581
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出版历程
- 收稿日期: 2007-09-25
- 刊出日期: 2008-03-25

Petrogenesis and Geological Implication of Serpentinized Peridotites in the Kokshal Segment, South Tianshan

1.
Xi'an Institute of Geology and Mineral Resource, China Geological Survey, Xi' an 710054, China
2.
State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
3.
Institute of Exploration and Development, Changqing Oilfield Company, Xi'an 710021, China

摘要

摘要: 巴雷公蛇绿混杂岩位于西南天山阔克萨彦岭地区, 代表了南天山古生代洋盆的洋壳残片.通过其中的地幔橄榄岩进行详细的地球化学研究, 分析其岩石成因及其形成环境.主量和微量元素特征显示巴雷公蛇纹石化橄榄岩Ti, Al含量低, Cr (1604~3863), Ni (1719×10^-6~2375×10^-6) 和Mg^#值(0.90~0.92) 高; 样品的稀土强烈亏损(ΣREE=0.28×10^-6~0.35×10^-6, Yb=0.1~0.11×CI), 呈宽缓的U型REE配分模式; 原始地幔标准化蛛网图显示, 强烈富集Rb、U和Sr, 从LILE (Cs、Rb、Ba、U、K和Sr) 到HREE, 元素含量自左向右随不相容性的逐渐降低, 呈右倾标准化微量元素配分型式; 橄榄岩熔融程度在20%~25%之间, 为俯冲带氧化条件下的熔融残留物.上述特征显示了俯冲板片流体与俯冲带上地幔楔物质的相互作用, 具有俯冲带型地幔橄榄岩特征.结合区域新获得的资料, 指示了南天山早古生代洋盆为一成熟的大洋, 早古生代曾发生过洋内俯冲作用.巴雷公蛇纹石化橄榄岩可能产生在南天山古生代洋内俯冲作用中的大洋岛弧的弧前地幔楔部位.
- 地幔橄榄岩 /
- 俯冲带 /
- 地幔熔融 /
- 巴雷公 /
- 阔克萨彦岭 /
- 南天山
Abstract: South Tianshan is a prominent intracontinental collisional orogenic belt and a key to understand the central Asia tectonic evolution.The serpentinized peridotites from Baleigong ophiolitic mélange was emplaced in the southwestern Kokshal area, which represents lithosphere remnants of the Early Paleozoic Southwestern Tianshan Ocean.The serpentinized peridotites are characterized by low Ti, Al contents and high Cr (1 604-3 863), Ni (1 719×10^-6-2 375×10^-6), Mg^# (0.90-0.92).The right slopping PUM-normalized trace element patterns and the U-shape chondrite-normalized REE pattern reveal that these rocks cannot be residues of simple melt extraction.They can be modeled as restites after 20%-30% partial melting from already depleted mantle in a supra-subduction zone (SSZ) geotectonic setting, in which a constant flux of a slab-derived fliud component added to the mantle wedge during melting.Combined with recent studies, it is concluded that the Paleozoic Southwestern Tianshan Ocean was a mature one that had even experienced a subduction event in Early Paleozoic.The serpentinized peridotites were formed at the fore-arc of the intra-oceanic subduction zone.
- mantle peridotite /
- supra-subduction zone /
- mantle melting /
- Baleigong /
- Kokshal /
- South Tianshan

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图 1 (a) 南天山构造轮廓图; (b) 巴雷公地区地质图

Fig. 1. (a) Locality, geological sketch map of South Tianshan orogenic belt; (b) geological map of the Baleigong

下载: 全尺寸图片幻灯片

图 2 MgO(无水)及相关元素关系图解

Fig. 2. Plots of abundance of variation elements against MgO (anhydrous)

下载: 全尺寸图片幻灯片

图 3 (a) 巴雷公蛇纹石化橄榄岩球粒陨石标准化稀土配分模式及(b)微量元素原始地幔标准化蛛网图

参考数据为1.Godard et al., (2000); 2.Melcher et al., (2002); 3.Hartmann and Wedepohl(1990); 4.Parkinson and Peare(1998); 球粒陨石数据引自Sun and McDonough (1989); PUM数据引自McDonough and Sun (1995)

Fig. 3. (a)Chondrite-normalized rare earth element diagrams and (b) whole rock multielement diagrams normalized toprimitive upper mantle(PUM, McDonough and Sun, 1995) for ultramafic samples of Baleigong

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图 4 (a) Si / (Mg+Fe) -Ca/ (Mg+Fe) (无水) 图解(El-Rus et al., 2006); (b) Si / (Mg+Fe) -LOI图解

Fig. 4. (a) Rock classification based on the relationship between the atomic ratios Si / (Mg+Fe) and Ca/ (Mg+Fe) (anhydrous) (El-Rus et al., 2006); (b) Si / (Mg+Fe) -LOI diagram

下载: 全尺寸图片幻灯片

图 5 巴雷公蛇纹石化橄榄岩的Yb-V图解(Pearce and Parkinson, 1993)

图中数字代表地幔熔融程度(%), V-Yb图解上面的落点表示不同氧逸度的熔融分馏趋势; QFM指铁橄榄石-磁铁矿-石英; QFM-1为还原条件下的部分熔融曲线; QFM+1为氧化条件下的部分熔融曲线

Fig. 5. Bivariate diagrams of Yb vs. V (in ppm) for residual peridotites, according to Pearce and Parkinson (1993)

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表 1 巴雷公蛇纹岩化橄榄岩主量元素(%) 和微量元素(μg/g) 化学分析组成

Table 1. Whole-rock major and trace element data for peridotites from Baleigong, South Tianshan

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