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引用本文:张超,吴新伟,张渝金,郭威,权京玉. 龙江盆地龙江组火山岩的地球化学特征及锆石U-Pb年龄[J]. 中国地质, 2018, 45(3): 456-468.
ZHANG Chao,WU Xinwei,ZHANG Yujin,GUO Wei,QUAN Jingyu. Geochemistry and zircon LA-ICP-MS U-Pb age of volcanic rocks in Longjiang Formation of Longjiang basin[J]. Geology in China, 2018, 45(3): 456-468(in Chinese with English abstract).
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龙江盆地龙江组火山岩的地球化学特征及锆石U-Pb年龄
张超1,2, 吴新伟1,2, 张渝金1,2, 郭威1,2, 权京玉3
1.中国地质调查局沈阳地质调查中心, 辽宁 沈阳 110034;2.吉林大学地球科学学院, 吉林 长春 130061;3.东北煤田地质局沈阳测试研究中心, 沈阳 110016
摘要:
在龙江盆地地区,龙江组由中—中酸性火山岩、火山碎屑岩和火山碎屑沉积岩组成。岩石地球化学显示为钙碱性岛弧火山岩系列,火山熔岩主体具有高SiO2、Na2O、Al2O3、Sr,低MgO、Y、Yb,和高场强元素Ta、Nb明显亏损等特征,与典型埃达克岩地球化学特征吻合,Sr和Sr/Y值显示为俯冲型埃达克岩。地球化学相关图解等表明岩浆在早期演化过程阶段可能发生了陆壳混染,经历了斜长石、辉石、铁钛氧化物和磷灰石的分离结晶作用。锆石LAICP-MS U-Pb谐和年龄为(125.9±1.5)Ma,与在该组中发现的化石资料完全一致,代表了火山岩的形成年龄。从东北地区火山岩的定年结果及其空间展布来看,龙江组火山岩的形成既与环太平洋构造体系有关,又与蒙古—鄂霍茨克构造带相联系。
关键词:  龙江盆地  龙江组  埃达克岩  锆石LA-ICP-MS U-Pb年龄
DOI:10.12029/gc20180303
分类号:P597.3;P588.14
基金项目:中国地质调查局项目(12120113053900、DD20160048-04、DD20160343-08、DD20160343-09)资助。
Geochemistry and zircon LA-ICP-MS U-Pb age of volcanic rocks in Longjiang Formation of Longjiang basin
ZHANG Chao1,2, WU Xinwei1,2, ZHANG Yujin1,2, GUO Wei1,2, QUAN Jingyu3
1.Shenyang Institute of Geology and Mineral Resources, CGS, Shenyang 110034, Liaoning, China;2.College of Earth Sciences, Jilin University, Changchun 130061, Jilin, China;3.Shenyang Tests Research Center, Northeast China Coal Field Geology Bureau, Shenyang 110016, Liaoning, China
Abstract:
The Longjiang Formation in Longjiang basin is composed of intermediate-acidic volcanic rocks, pyroclastic rocks and tuffaceous sedimentary rocks. The petrochemical compositions of most volcanic rocks belong to the calc-alkaline island arc series. These volcanic rocks are characterized by high SiO2, Na2O, Al2O3 and Sr content, low MgO, Y and Yb content and clear depletion of high field strength elements (Ta, Nb), similar to the characteristics of the classical adakite. These Sr values and Sr/Y ratios are also similar or close to features of most subduction-type adakites. Geochemical characteristics indicate that the magma experienced crust contamination and fractional crystallization of clinipyroxene, plagioclase, Ti-Fe-oxides and apatite during the early evolution process. The zircon LA-ICP-MS U-Pb age is 125.9±1.5Ma, consistent with the fossils data, representing volcanics formation age. Combined with the spatial variation of ages of the Mesozoic volcanic rocks in Northeast China, the authors hold that the formation of the volcanic rocks was related to the Circum-Pacific tectonic system as well as the Mongolia-Okhotsk structural belt.
Key words:  Longjiang basin  Longjiang Formation  adakite  zircon LA-ICP-MS U-Pb dating