Chronology and Geochemistry of Volcanic Rocks in the Cretaceous Suifenhe Formation in Eastern Heilongjiang, China
Chronology and Geochemistry of Volcanic Rocks in the Cretaceous Suifenhe Formation in Eastern Heilongjiang, China
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DOI：
10.1111/j.1755-6724.2007.tb00950.x
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发表时间：
2007-04
期刊：
影响因子：
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通讯作者：
Weiqiang Ji;Wenliang Xu;Yang Debin;F. Pei;Jin Ke;Xiaoming Liu
中科院分区：
文献类型：
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作者：
Weiqiang Ji;Wenliang Xu;Yang Debin;F. Pei;Jin Ke;Xiaoming Liu
文摘：报道了黑龙江省东部绥芬河组火山岩的锆石U-Pb年龄和地球化学数据，并对其成因进行了探讨。绥芬河组主要由玄武岩、安山岩和英安岩组成。安山岩和英安岩中的锆石呈自面体状，呈典型的振荡分带，Th/U值高(0.18~0.57)，表明其为岩浆成因。激光烧蚀电感耦合等离子体质谱(LA-ICPMS)的锆石U-Pb定年结果表明，安山岩中锆石的206Pb/238U年龄范围为10 5~10 6 Ma，加权平均年龄为105.5±0.8 Ma(n=14)；英安岩中锆石的206Pb/238U年龄为90~96 Ma，加权平均年龄为93.2±1.3 Ma(n=13)。绥芬河组火山岩属亚碱性系列，呈钙碱性演化趋势，SiO_2含量为47.69%~65.47%，镁含量为1.42%~6.80%(Mg−=45~53)，Na_2O/K_2O比值为1.83~3.63。它们的特征是富含大离子亲石元素(LILE)和轻稀土元素(LREE)，亏损重稀土元素(HREE)和高场强元素(如Nb、Ta、Ti)，初始87Sr/86Sr比值(0.7041~0.7057)和正值(0.39~4.08)，表明它们可能来自亏损的岩浆源区。这些结果表明，火山岩的原生岩浆可能起源于活动大陆边缘构造背景下俯冲板块流体交代的地幔楔体的部分熔融。
Abstract: Zircon U‐Pb ages and geochemical data of volcanic rocks in the Suifenhe Formation in eastern Heilongjiang Province are reported, and their petrogenesis is discussed in this paper. The Suifenhe Formation mainly consists of basalt, andesite, and dacite. Zircon from andesite and dacite are euhedral in shape and show typical oscillatory zoning with high Th/U ratios (0.18‐0.57), implying its magmatic origin. Zircon U‐Pb dating results by laser ablation inductively coupled plasma mass spectrometer (LA‐ICP‐MS) indicate that the 206Pb/238U ages of zircons from andesite range within 105–106 Ma, yielding a weighted mean age of 105.5±0.8 Ma (n=14), and that 206Pb/238U ages of zircons from dacite are between 90–96 Ma, yielding a weighted mean age of 93.2±1.3 Ma (n =13). The volcanic rocks from the Suifenhe Formation are subalkaline series and show a calc‐alkaline evolutionary trend with SiO2 content of 47.69%‐65.47%, MgO contents of 1.42%‐6.80% (Mg− = 45–53), and Na2O/K2O ratios of 1.83‐3.63. They are characterized by enrichment in large ion lithophile elements (LILE) and light‐rare‐earth elements (LREE), depletion in heavy rare earth elements (HREE) and high field strength elements (HFSE) (e.g., Nb, Ta, Ti), and low initial 87Sr/86 Sr ratios (0.7041‐0.7057) and positive øNd(t) values (0.39‐4.08), implying that they could be derived from a depleted magma source. Taken together, these results suggest that the primary magma of the volcanic rocks might originate from partial melting of the mantle wedge metasomatized by fluids derived from subducted slab under a tectonic setting of active continental margin.