| 浙西北地区晚中生代花岗岩的岩石成因 |
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| 引用本文： | 唐增才,周汉文,胡开明,陈忠大,吴小勇,胡文杰,董学发,赵旭东,余盛强,张建芳.浙西北地区晚中生代花岗岩的岩石成因[J].地球科学,2019,44(4):1278-1294. |
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| 作者姓名： | 唐增才 周汉文 胡开明 陈忠大 吴小勇 胡文杰 董学发 赵旭东 余盛强 张建芳 |
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| 作者单位： | 1.浙江省地质调查院, 浙江杭州 311203 |
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| 基金项目： | 浙江省国土资源厅项目2007002中国地质调查局地质调查项目1212011120834浙江省国土资源厅项目2010001中国地质调查局地质调查项目12120114068901浙江省国土资源厅项目2014004中国地质调查局地质调查项目1212011220527 |
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| 摘 要： | 浙西北地区晚中生代处于环太平洋活动大陆边缘，区内岩浆侵入活动强烈，发育Ⅰ型和铝质A型两类花岗岩，前者又分为低分异Ⅰ型（简称Ⅰ型）和高分异Ⅰ型花岗岩两种，形成时限为中侏罗世-早白垩世早期（172~135 Ma），其中高分异Ⅰ型花岗岩集中于早白垩世早期（147~135 Ma）；铝质A型花岗岩形成于早白垩世中期（135~123 Ma）.同位素地球化学研究表明，中侏罗世-早白垩世早期Ⅰ型花岗岩（87Sr/86Sr）i值为0.707 004~0.711 896，εNd（t）值为-6.70~-2.00，锆石εHf（t）值为-5.08~-1.67，TDMC值为1 162~1 358 Ma，系古太平洋板块俯冲挤压的构造环境下，少量幔源物质沿变向俯冲引起的板片裂隙（窗）与下地壳重熔岩浆混合作用的产物；晚侏罗世末期-早白垩世早期高分异Ⅰ型花岗岩（87Sr/86Sr）i为0.706 890~ 0.709 880，εNd（t）值为-6.80~-4.50，锆石εHf（t）为-6.59~-5.23，TDMC为1 350~1 423 Ma，是古太平洋板块撤离机制下挤压向伸展转换的产物，系软流圈上涌诱发的幔源基性岩浆与中元古代地壳物质的部分熔融形成长英质岩浆混合并经高程度分异演化形成；早白垩世中期铝质A型花岗岩（87Sr/86Sr）i值为0.703 503~0.710 171，εNd（t）值为-8.90~-0.30，锆石εHf（t）值为-9.70~2.48，TDMC值为734~1 593 Ma，为岩石圈持续减薄机制下，越来越多的幔源物质（或新生地壳）涌入深部长英质岩浆房混合形成.
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| 关 键 词： | 动力学背景 岩石成因 地球化学 花岗岩 晚中生代 浙西北 |
| 收稿时间： | 2018-04-12 |
Petrogenesis of Late Mesozoic Granites in Northwest Zhejiang |
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| Abstract: | The strong Late Mesozoic magmatic intruding events happened in Northwest Zhejiang area, which is located in the active western Pacific margin. The granites are classified as Ⅰ- and aluminous A-types, and the former is further divided into Ⅰ-type and highly fractionated Ⅰ-type granites. The Ⅰ-type granites of Mid-Late Jurassic to early Early Cretaceous(172-135 Ma) have the initial 87Sr/86Sr ratios ranging from 0.707 004 to 0.711 896, εNd(t) values from -6.70 to -2.00, εHf(t) values from -5.08 to -1.67, indicating that these granites are originated from mixing between remelted Meso-Neoproterozoic Jiangnan island arc and little mantle materials rose along slab crack. The formation of these granites may be closely related to the subduction of Paleo-Pacific plate. The highly fractionated Ⅰ-type granites in the early Early Cretaceous(147-135 Ma) have the initial 87Sr/86Sr ratio ranging from 0.706 890 to 0.709 880, εNd(t) values from -6.80 to -4.50, εHf(t) values from -6.59 to -5.23, suggesting that they are the products of magma mixing by remelting crustal materials of the Meso-Neoproterozoic and rising mantle mafic magma due to asthenosphere uplifting. It also indicates that the tectonic environment transformed from compression to extension in this period.The A-type granites of middle Early Cretaceous(135-123 Ma) have the initial 87Sr/86Sr ratios ranging from 0.703 503 to 0.710 171, εNd(t) values from -8.90 to -0.30, εHf(t) values from -9.70 to 2.48, indicating that the magma during Middle-Early Cretaceous was mainly originated from remelting of the Meso-Neoproterozoic crustal materials, mixed by more and more mantle materials, in an extension setting. |
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