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| 1 | 再论花岗岩按照Sr-Yb的分类:标志显示文摘2006年作者曾经按照Sr=400×10^(-6)和Yb=2×10^(-6)作为标志将花岗岩分为埃达克岩、喜马拉雅型花岗岩、浙闽型花岗岩和广西型花岗岩,在浙闽型中又分出南岭型(Sr<100×10^(-6)和Yb>2×10^(-6)),于是花岗岩被分为5类。Sr=400×10^(-6)和Yb=2×10^(-6)是根据阿留申群岛中的Adak岛的资料得出来的。本文统计了全球花岗岩6000多个数据(其中,埃达克型花岗岩为2810个,喜马拉雅型花岗岩636个,浙闽型花岗岩1183个,南岭型花岗岩1518个,广西型花岗岩142个,总共6289个),统计的结果,各类花岗岩的地球化学特征大致如下:(1)埃达克型花岗岩富Al_2O_3和Sr,贫Y和Yb,具较高和变化的铕异常,绝大多数样品的Sr>300×10^(-6),Yb<2.5×10^(-6)(当Sr=400×10^(-6)~600×10^(-6)时Yb值最大,Sr超过600×10^(-6),Yb降低至<2×10^(-6)),Al_2O_3在14%~18%之间,Eu/Eu~*大多在0.6~1.2范围;(2)喜马拉雅型花岗岩贫Sr和Yb,具中等的Al_2O_3和变化的Eu/Eu~*,Sr<300×10^(-6)和Yb<2×10^(-6)(少数Sr>300×10^(-6)),Al_2O_3为13%~17%,Eu/Eu~*为0.2~1.0;(3)浙闽型花岗岩贫Sr富Yb,Sr在40×10^(-6)~400×10^(-6)之间,Yb>1.5×10^(-6),Al_2O_3和Eu/Eu~*的变化类似喜马拉雅型花岗岩,Al_2O_3为12%~17%,Eu/Eu~*为0.4~1.0;(4)南岭型花岗岩以很低的Sr、Al_2O_3和Eu/Eu~*以及很高的Yb而不同于上述各类花岗岩,通常Yb>1.5×10^(-6),Sr<100×10^(-6)(Yb变化大,绝大多数>2×10^(-6);当Yb在2×10^(-6)~8×10^(-6)时,部分样品Sr可>100×10^(-6),但很少>200×10^(-6));Al_2O_3<14%,集中在11%~13%之间,Eu/Eu~*<0.7,大多<0.4;Yb越大,Sr越低,负铕异常越明显。文中讨论了花岗岩Sr-Yb分类的意义,指出本分类适用于产于大陆和海洋的绝大多数中酸性岩浆岩(可能不适用于一部分特别富铁和钾的花岗岩,如具有高Sr和Yb特征的广西型花岗岩)。不同类型的花岗岩主要反映了源区压力的不同,而源区成分、温度、部分熔融程度、水和挥发分的加入以及岩浆混合等的影响可能是次要的。文中指出,该分类的依据、其实质,是熔体与残留相平衡的理论。与浙闽型花岗岩平衡的残留相是斜长石,与喜马拉雅型花岗岩平衡的是斜长石+石榴石,与埃达克型花岗岩平衡的是石榴石,与南岭型花岗岩平衡的是富钙的斜长石。文中指出,加强实验岩石学研究,将年代学和地球化学研究密切结合起来是深化花岗岩研究的关键。 | 张旗 金惟俊 李承东 王元龙 | 2010 | 岩石学报2010，26，4： | 158 |
| 2 | Paleoproterozoic crustal evolution of the Hengshan-Wutai—Fuping region,North China Craton显示文摘An arguable point regarding the Neoarchean and Paleoproterozoic crustal evolution of the North China Craton(NCC)is whether the tectonic setting in the central belt during the mid-Paleoproterozoic(2.35-2.0 Ga)was dominated by an extensional regime or an oceanic subduction-arc regime.A review of the midPaleoproterozoic magmatism and sedimentation for the Hengshan-Wutai-Fuping region suggests that a back-arc extension regime was dominant in this region.This conclusion is consistent with the observation that the 2.35-2.0 Ga magmatism shows a typical bimodal distribution where the mafic rocks mostly have arc affinities and the acidic rocks mainly comprise highly-fractioned calc-alkaline to alkaline(or A-type)granites,and that this magmatism was coeval with development of extensional basins characteristic of transgressive sequences with volcanic interlayers such as in the Hutuo Group.Although the final amalgamation of the NCC was believed to occur at ~1.85 Ga,recent zircon U-Pb age dating for mica schist in the Wutai Group suggests a collisional event may have occurred at ~1.95 Ga.The metamorphic ages of ~1.85 Ga,obtained mostly from the high-grade rocks using the zircon U-Pb approach,most probably indicate uplifting and cooling of these high-grade terranes.This is because(i)phase modeling suggests that newly-grown zircon grains in highgrade rocks with a melt phase cannot date the age of peak pressure and temperature stages,but the age of melt crystallization in cooling stages;(ii)the metamorphic P-T paths with isobaric cooling under 6-7 kb for the Hengshan and Fuping granulites suggest their prolonged stay in the middle-lower crust;and(iii)the obtained metamorphic age data show a continuous distribution from 1.95 to 1.80 Ga.Thus,an alternative tectonic scenario for the Hengshan-Wutai-Fuping region involves:(i)formation of a proto-NCC at ~2.5 Ga;(ii)back-arc extension during 2.35-2.0 Ga resulting in bimodal magmatism and sedimentation in rifting basins on an Archean basement;(iii)a crustal thickening event in the extended region resulting in a kyanitetype metamorphism at ~1.95 Ga,and(iv) uplifting and cooling of the thickened crust from 1.93 to 1.80 Ga. | Chunjing Wei Jiahui Qian Xiwen Zhou | 2014 | Geoscience Frontiers2014，5，4： | 32 |
| 3 | 华北中部造山带五台-恒山地区古元古代变质作用与构造演化显示文摘华北克拉通古元古代造山带的时空分布与构造属性尚有很大争论,一种观点认为华北克拉通从新太古代至古元古代受大洋俯冲闭合控制,在1.85~1.95Ga之间先后发生3次陆-陆碰撞形成3条造山带,即孔兹岩带、胶-辽-吉带和中部造山带;另一种观点强调华北克拉通这3条元古代造山带在1.80~1.98Ga之间经历了相同的漫长演化过程,指示当时特有的热俯冲和碰撞环境.通过总结中部造山带中的五台-恒山地区变质作用研究进展,阐述该区古元古代造山时代与构造属性.五台-恒山地区的主要变质岩石-构造单元包括恒山杂岩、五台杂岩和滹沱群.恒山杂岩和五台杂岩主体为新太古代TTG片麻岩和表壳岩,它们在古元古代晚期经历了两期变质作用改造.第一期变质作用为中压型,是由于陆-陆碰撞导致弧后伸展盆地闭合、地壳加厚造山所致,从南向北形成一个递增序列:包括五台群下部和南恒山杂岩南部的低角闪岩相、南恒山杂岩北部高角闪岩相和北恒山杂岩的高压麻粒岩相,其压力峰期所对应的地热梯度为~15℃/km.变质锆石所记录的年龄峰值随着变质程度增高而降低,依次为~1.95Ga、~1.92Ga和~1.85Ga,这是因为在变质过程中锆石生长受流体和熔体行为控制:在亚固相线下,变质锆石可记录峰期变质年龄,而在超固相线条件下记录伴随熔体结晶的退变质年龄.由此确定该区中压相系变质作用压力峰期时间为~1.95Ga,对应地壳加厚造山的峰期.加厚地壳由于重力均衡导致变质岩从深部地壳折返至中部地壳,在P-T轨迹上表现为压力峰期之后发生等温减压(ITD)至0.5~0.7GPa,岩相学上表现为峰期石榴石分解形成斜长石'白眼圈'等,指示缺流体条件.南恒山北部高角闪岩相岩石中的变质锆石记录的折返时间为~1.92Ga,指示第一次造山结束.第二期变质作用为中-低压型,系为板内变形所致,表现为折返至中地壳的岩石伴随挤压型剪切变形和流体注入形成平衡矿物组合.朱家坊韧性剪切带就是这次板内变形的强构造域,其中也记录了顺时针型P-T轨迹,但所反映的地壳加厚程度有限,第二期变质-变形峰期时间为~1.85Ga.由于朱家坊韧性剪切带左行走滑,导致北恒山麻粒岩地体抬升.五台-恒山地区在1.80~1.96Ga之间经历两期变质-变形事件,这一认识或对讨论华北克拉通其他地区的古元古代造山带演化有一定启示意义. | 魏春景 | 2018 | 地球科学2018，43，1： | 27 |
| 4 | Neoarchean(2.5-2.8 Ga) crustal growth of the North China Craton revealed by zircon Hf isotope:A synthesis显示文摘The crustal growth of the North China Craton(NCC) during the Neoarchean time(2.5—2.8 Ga) is a hotly controversial topic,with some proposing thai the main crustal growth occurred in the late Neoarchean (2.5—2.6 Ga),in agreement with the time of the magmatism,whereas others suggest that the main crustal accretion took place during early Neoarchean time(2.7—2.8 Ga),consistent with the time of crustalformation of other cratons in the world.Zircon U-Pb ages and Hf isotope compositions can provide rigorous constraints on the time of crustal growth and the evolution and tectonic division of the NCC.In this contribution, we make a comprehensive review of zircon Hf isotope data in combination with zircon U-Pb geochronology and some geochemistry data from various divisions of the NCC with an aim to constrain the Neoarchean crustal growth of the NCC.The results suggest that both 2.7—2.8 Ga and 2.5—2.6 Ga crustal growth are distributed over the NCC and the former is much wider than previously suggested.The Eastern block is characterized by the main 2.7—2.8 Ga crustal growth with local new crustal-formation at 2.5—2.6 Ga,and the Yinshan block is characterized by~2.7 Ga crustal accretion as revealed by Hf-isotope data of detrital zircons from the Zhaertai Group.Detrital zircon data of the Khondalite Belt indicate that the main crustal growth period of the Western block is Paleoproterozoic involving some~2.6 Ga and minor Early- to Middle-Archean crustal components,and the crustal accretion in the Trans-North China Orogen(TNCO) has a wide age range from 2.5 Ga to 2.9 Ga with a notable regional discrepancy.Zircon Hf isotope compositions,coupled with zircon ages and other geochemical data suggest that the southern margin may not be an extension of the TNCO,and the evolution and tectonic division of the NCC is more complex than previously proposed,probably involving multi-stage crustal growth and subduction processes.However, there is no doubt that 2.7—2.8 Ga magmatism and crustal-formation are more widely distributed than previously considered,which is further supported by the data of zircons from Precambrian lower crustal rocks, overlying sedimentary cover,modern river sediments and Late Neoarchean syenogranites. | Andong Wang Yican Liu | 2012 | Geoscience Frontiers2012，3，2： | 25 |
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