Contrasting Late Carboniferous and Late Permian–Middle Triassic intrusive suites from the northern margin of the North China craton: Geochronology, petrogenesis, and tectonic implications
Contrasting Late Carboniferous and Late Permian–Middle Triassic intrusive suites from the northern margin of the North China craton: Geochronology, petrogenesis, and tectonic implications
复制标题
DOI：
10.1130/b26157.1
复制
发表时间：
2006
影响因子：
4.9
通讯作者：
Shuan‐Hong Zhang;Yue Zhao;B. Song;Jianmin Hu;Shuwen Liu;Yue-heng Yang;Fukun Chen;Xiaoming Liu-Xiaoming-L
中科院分区：
文献类型：
--
作者：
Shuan‐Hong Zhang;Yue Zhao;B. Song;Jianmin Hu;Shuwen Liu;Yue-heng Yang;Fukun Chen;Xiaoming Liu-Xiaoming-L
在华北克拉通北方边缘发现了两套不同的侵入岩：一套为晚石炭世闪长岩-花岗闪长岩，主要由石英闪长岩、闪长岩、花岗闪长岩、英云闪长岩和角闪辉长岩组成;另一套为晚二叠世-中三叠世花岗岩类侵入岩，主要由二长花岗岩、正长花岗岩和石英二长岩组成。晚石炭世岩套中的岩体具有SiO2含量变化大、钙碱性或高钾钙碱性、变光等地球化学特征。大部分的全岩Nd（T）值（其中T为结晶年龄）较低，为−17.1至−11.5，锆石Hf（T）值为−38.3至−11.2，表明它们主要来自古老下地壳的深源熔融，并有一些地幔物质的参与。然而，该岩套中的一个较老的岩体显示出较高的εNd（T）值（−11.5至−9.9），Nd模式年龄（1.82-1.64 Ga），较低的87 Sr/86 Sr初始比值（0.7046-0.7048），并且它含有一些锆石颗粒，其特征是具有较高的负到正锆石εHf（T）值（−8.7至1.2），表明强烈的年轻的物质来自岩石圈地幔的参与。晚石炭世的岩体被解释为俯冲有关，并已侵位在安第斯风格的大陆边缘弧在向南俯冲的古亚洲大洋板块下的华北克拉通。晚二叠世-中三叠世侵入岩套的岩石显示出从高度分馏的I型到A型的地球化学特征。它们的锆石Hf（T）值为−14.9至−6.7，全岩Hf（T）值为−10.6至−8.8，Hf和Nd模式年龄比大多数晚石炭世岩体都要年轻，这表明它们可能是由同时代地幔和地壳来源的熔体混合而产生的混合岩浆的极端分离结晶作用产生的。它们被解释为后碰撞/后造山花岗岩类与岩石圈伸展和软流圈上涌，由于板片断裂和随后的下沉后，最终碰撞和蒙古弧岩与中国北方克拉通。这两个对比鲜明的侵入岩套表明，古亚洲洋的最终闭合以及蒙古弧地体与华北克拉通之间的碰撞发生在晚二叠世，这些事件随后发生了碰撞后/造山后伸展、大规模岩浆活动和显着的大陆生长。在碰撞过程中没有发生明显的同碰撞地壳增厚、高压变质作用和S型花岗岩类岩浆活动。
Two contrasting intrusive suites have been identified from the northern margin of the North China craton: a Late Carboniferous dioritegranodiorite suite mainly made up of quartz diorite, diorite, granodiorite, tonalite, and hornblende gabbro, and a Late Permian–Middle Triassic suite of granitoid intrusions consisting of monzogranite, syenogranite, and quartz monzonite. Plutons from the Late Carboniferous suite exhibit variable SiO2 contents and calc-alkaline or high-K calc-alkaline, metaluminous geochemical features. Most have low negative whole-rock ϵNd(T) values (where T is the crystallization age) of −17.1 to −11.5 and zircon ϵHf(T) values of −38.3 to −11.2, indicating that they were derived mainly from anatectic melting of the ancient lower crust with some involvement of mantle materials. However, an older pluton in the suite exhibits higher ϵNd(T) values of −11.5 to −9.9, Nd model ages of 1.82–1.64 Ga, lower initial 87Sr/86Sr ratios of 0.7046–0.7048, and it contains some zircon grains that are characterized by high negative to positive zircon ϵHf(T) values of −8.7 to 1.2, indicating strong involvement of juvenile materials derived from the lithospheric mantle. The Late Carboniferous plutons are interpreted as subduction-related and to have been emplaced in an Andean-style continental-margin arc during the southward subduction of the paleo–Asian oceanic plate beneath the North China craton. Rocks from the Late Permian–Middle Triassic intrusive suite display geochemical signatures ranging from highly fractionated I-type to A-type. They exhibit higher zircon ϵHf(T) values of −14.9 to −6.7, whole-rock ϵNd(T) values of −10.6 to −8.8, and younger Hf and Nd model ages than most of the Late Carboniferous plutons, indicating that they could have been produced by extreme fractional crystallization of hybrid magmas resulted from mixing of coeval mantle- and crust-derived melts. They are interpreted as postcollisional/postorogenic granitoids linked to lithospheric extension and asthenosphere upwelling due to slab break-off and subsequent sinking after final collision and suturing of the Mongolian arc terranes with the North China craton. These two contrasting intrusive suites suggest that the final closure of the paleo–Asian Ocean and collision between the Mongolian arc terranes and the North China craton occurred during the Late Permian, and these events were followed by postcollisional/postorogenic extension, large-volume magmatism, and significant continental growth. No significant syncollisional crustal thickening, high-pressure metamorphism, or S-type granitoid magmatism occurred during the collision process.