Platinum-group element geochemistry of Cenozoic basalts from the North China Craton: Implications fo

来源 :Science China(Earth Sciences) | 被引量 : 0次 | 上传用户:mario0798
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
Forty-two Cenozoic(mostly Miocene) basalt samples from Jining, Chifeng, Fansi, Xiyang, and Zuoquan areas of the North China Craton(the NCC basalts hereafter) were analyzed for platinum-group elements(PGE, including Os, Ir, Ru, Rh, Pt, and Pd). Most of them are alkaline basalts and tholeiites and all of them display little crustal contamination. The total PGE contents of the NCC basalts vary from 0.1 to 0.9 ppb, much lower than those of the primitive mantle values of 23.5 ppb. Primitive mantle-normalized PGE patterns of these basalts define positive slopes and Pd/Ir ratios vary from 1.2 to 25. In terms of both PGE contents and Pd/Ir ratios, they are quite similar to the mid-ocean ridge basalts. There are no obvious negative correlations between PGE vs. Mg O, Ni, and Cu in the NCC basalts, indicating that fractional crystallization of olivine, pyroxene, and/or sulfides during magmatic process cannot be the controlling factor for the observed PGE variation. The observed Pd/Ir variations of the NCC basalts require involvement of non-chondritic heterogeneous mantle sources. Based on Sr-Nd-Pb-Hf isotopic systematics and incompatible-element signatures, a mixing of partial melts from both asthenospheric peridotites and enclosed mantle eclogites at the top of asthenosphere was proposed for the origin of these NCC basalts. The lenses of eclogites are derived from upwelling of recycled continental crust during the westward subduction of the Pacific plate from the ~600 km discontinuity zone. The PGE geochemistry of these basalts provides independent evidence to support this conclusion and the observed Pd/Ir variations may reflect variations in proportions of tapped peridotitic and eclogitic melts. Forty-two Cenozoic (mostly Miocene) basalt samples from Jining, Chifeng, Fansi, Xiyang, and Zuoquan areas of the North China Craton (the NCC basalts hereafter) were analyzed for platinum-group elements (PGE, including Os, Ir, Ru, Rh, Pt, and Pd). Most of them are alkaline basalts and tholeiites and all of them display little crustal contamination. The total PGE contents of the NCC basalts vary from 0.1 to 0.9 ppb, much lower than those of the primitive mantle values ​​of 23.5 ppb. Primitive mantle-normalized PGE patterns of these basalts define positive slopes and Pd / Ir ratios vary from 1.2 to 25. In terms of both PGE contents and Pd / Ir ratios, they are quite similar to the mid-ocean ridge basalts. There are no obvious negative correlations between PGE vs. MgO, Ni, and Cu in the NCC basalts, indicating that fractional crystallization of olivine, pyroxene, and / or sulfides during magmatic process can not be the controlling factor for the observed PGE variation. observed Pd / Ir variations o based on Sr-Nd-Pb-Hf isotopic systematics and incompatible-element signatures, a mixing of partial melts from both asthenospheric peridotites and enclosed mantle eclogites at the top of asthenosphere was proposed for the origin of these NCC basalts. The lenses of eclogites are derived from upwelling of recycled continental crust during the westward subduction of the Pacific plate from the ~ 600 km discontinuity zone. The PGE geochemistry of these basalts provides independent evidence to support this conclusion and the observed Pd / Ir variations may reflect variations in proportions of tapped peridotitic and eclogitic melts.
其他文献
词是音与义的结合体,是能够独立运用的最小的语言单位。就同本身来讲,它包含表达事物概念的本义和引申义。在句子中,不同的词语按语法关系可以组合在一起。词的词汇意义只表示本
典型的甲状腺功能亢进性心脏病(甲亢心)临床易诊断,但若临床表现不典型,仅以心血管系统方面的表现为主,容易误诊误治,尤其在基层医院。笔者所在医院自2004年2月至2008年8月诊
据最近对怀化地区两家中心支行和18个县级支行的稽查了解,银行的金融资产负债情况在会计报表上没有得到真实的反映,其状况令人担忧:一是隐瞒存款,漏缴、少缴人行存款准备金
本成果挤压铸焊工艺研制了嵌焊钢环式接线端子及嵌焊铜板条式并沟线夹。前者的铜件是带外环沟槽和螺栓孔的环 ;后者的铜件是带半圆沟槽的梯形板条。铜件焊接面经特殊处理后 ,
目的:探讨腹腔妊娠的诊断以及治疗方案,以提高对该病的认识、降低患者死亡率以及减少产后并发症。方法:回顾性分析和总结我院收治的1例原发性腹腔妊娠的诊断及治疗方案。结果
近日,Kuali基金会宣布HTC全球服务公司作为企业投资合伙人与Kuali OLE(开放图书馆环境)建立合作关系。Kuali OLE是一个健壮的、开源的、易用的企业级系统,用于选择、获取、描
http://www.bbc.co.uk印度国家核能机构首席官员班纳吉(Banerjee)称,印度南部的安德拉邦有望成为世界上最大的铀矿基地之一。据印度官方的报道,杜姆拉帕(Tummalapalle)铀矿位
在西方发达国家,注册会计师制度经过长期发展,已经形成一个较完善、行之有效的体系。美国的注册会计师制度已有100多年的历史。罗斯福总统曾高度评价CPA是“最受信赖的职业之一
我国高校图书馆的社会化服务相比于欧美发达国家起步较晚,发展速度也相对缓慢,然而随着广大人民群众对科技知识的需求量日益增大,高校图书馆走向社会化将是大势所趋。本文通
20世纪的最后一年脚步匆匆,转瞬即逝,在迎来新世纪曙光之际,让我们共同回顾译坛。 ’ 99年全国性的翻译学术活动频繁: 3月在天津举行了全国第四次大中型企业翻译研讨会;5月在重庆的“语