摘要
西准噶尔地区广泛发育高镁质闪长质岩墙。对全岩样品的Ar-Ar测年获得了321Ma的坪年龄,显示其主要形成于石炭纪末。这些岩墙样品以富Si(SiO252.3%～56.9%)、Mg(Mg#>60)、Cr(134～204μg/g)、Ni(59～141μg/g)、Sr(468～724μg/g)、Ba(316～676μg/g)为特征且K/Na比值在0.38～0.63之间,类似于日本中新世Setouchi火山岩带中的赞岐岩。这些岩墙大多具有不同程度的Eu正异常并具有高的Ba/La比值(27～124),反映其主要来自消减带环境下受流体交代的地幔源区的部分熔融。赞岐岩和区内同时代埃达克质岩石的共生组合意味着该区在晚石炭世末曾受到热消减机制的影响。这种热的洋壳俯冲机制,不仅在石炭纪末期产生了大量的岩浆活动,而且也导致了铜金等成矿元素的富集。深入了解赞岐岩-埃达克岩共生组合与铜金矿化之间的密切关系将有助于正确评价区内成矿潜力。
High-Mg dioritic dykes widely occur in the western Junggar, Xinjiang and recorded the Late Paleozoic tectonic evolutionary history of the area. Whole-rock Ar-Ar dating on the dykes has yielded a plateau age of 321 Ma, indicating their formation at the end of the Carboniferous. The dykes are enriched in Si （SiO2 52.3% - 56.9% ）, and characterized by high Mg （Mg# 〉 60）, Cr （134 -204μg/g）, Ni （59 - 141μg/g）, Sr （468 -724 μg/g） and Ba （316 - 676 μg/g） contents, with geochemical features analogous to those of sanukite in Setouchi volcanic belt, Japan. The dykes generally display high Ba/La （27 - 124）, and positive Eu anomalies, indicating their origination from hydrous partial melting of a mantle source metasomatised by fluid. The occurrence of sanukitic dykes, together with the coeval slab-related adakite in the area, implies the western Junggar had been affected by hot, subduction-related regime, which gave rise to not only massive magmatism in the late Carboniferous, but also wide mineralization of Cu and Au. A profound, comprehensive research is required to explore the intimate relationship between the sanukite-adakite association and the potential Cu-Au mineralization in the region.
出处
《地球化学》
CAS
CSCD
北大核心
2009年第5期413-423,共11页
Geochimica
基金
国家重点基础研究发展计划项目(2007CB411308)
国家自然科学基金(40421303
40772130)
中国科学院国际合作伙伴计划项目
香港RGC项目(HKU7040/04P)
