Petrology, geochronology and geochemistry of ca. 780 Ma A-type granites in South China: Petrogenesis and implications for crustal growth during the breakup of the supercontinent Rodinia
Petrology, geochronology and geochemistry of ca. 780 Ma A-type granites in South China: Petrogenesis and implications for crustal growth during the breakup of the supercontinent Rodinia
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DOI：
10.1016/j.precamres.2010.02.004
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发表时间：
2010-04
影响因子：
3.8
通讯作者：
Qiang Wang;D. Wyman;Zheng‐Xiang Li;Z. Bao;Zhenhua Zhao;Yixian Wang;P. Jian;Yue-heng Yang;
中科院分区：
文献类型：
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作者：
Qiang Wang;D. Wyman;Zheng‐Xiang Li;Z. Bao;Zhenhua Zhao;Yixian Wang;P. Jian;Yue-heng Yang;
华南陆块广泛发育新元古代（830- 740 Ma）钙碱性侵入岩，被认为是前寒武纪Rodinia超大陆的一部分。然而，这些岩石的构造背景仍然存在争议。两种截然不同的解释，大陆裂谷或火山弧环境，意味着不同的位置华南在Rodinian重建。同样不清楚的是，如此大规模的岩浆活动是如何导致地壳显著增长的。本研究提供了CA的数据。华南北方道林山地区780 Ma A型花岗岩相对较早的花岗岩矿物组合包括钾镁矾、铁黄长石、锆石、含钛磁铁矿、钛铁矿、氟磷灰石和/或铁橄榄石±铁钠闪石，相对较晚的矿物组合包括条纹长石、铁硅闪石、钠闪石±铁钠闪石、石英、钠长石、钛铁矿、金红石、磁铁矿、菱铁矿、绿柱石和角闪石。萤石和方解石出现在所有阶段。花岗岩具有低的Al 2 O3、Eu、Ba和Sr含量，高的Na 2 O + K2 O、Zr+Nb+Ce+Y、10,000×Ga/Al和Zr值，高的FeOT/（FeOT+MgO）（0.90-0.95）比值，与典型的A型花岗岩相似。它们也具有高的全岩Nd（t）值（+3.6至+6.2）和锆石Hf（t）（+6.7至+17.4）。温度和氧逸度（[公式：见正文]）估计表明，北方道林山A型花岗质岩浆是在高温（960-990°C）、低[公式：见正文]（在或略高于铁橄榄石-磁铁矿-石英（FMQ）缓冲层）、富F和CO2但极贫H2O的条件下生成的，表明岩浆形成的裂谷环境而不是弧环境。根据区内新元古代及更古老的火成岩的成分、年代学和Hf同位素资料，我们认为北方道林山花岗岩很可能是由下地壳中稍早的拉斑玄武岩在约780 Ma的高温地幔柱作用下发生高温熔融而形成的。这一结果支持了华南从劳伦提斯裂谷离开是由一个约1000年前的裂谷作用引起的假说。780 Ma Rodinia裂解期地幔柱。华南新元古代（830- 740 Ma）地幔柱活动也引起了广泛的地壳生长。
There are widespread Neoproterozoic (830–740Ma) calc-alkaline intrusive rocks in the South China Block, which has been considered a part of the Precambrian supercontinent Rodinia. The tectonic setting of these rocks, however, remains in dispute. Two distinctly different interpretations, continental rift or volcanic arc settings, imply different positions for South China in the Rodinian reconstruction. It is also unclear how such a large-scale magmatic event led to significant crustal growth. This study presents data for ca. 780Ma A-type granites in the northern Daolinshan area, South China. A relatively early granite mineral assemblage contains katophorite, ferrorichterite, zircon, titaniferous magnetite, ilmenite, fluorapatite, and/or fayalite±arfvedsonite, and a relatively late mineral assemblage consists of perthite, ferrowinchite, riebeckite±arfvedsonite, quartz, albite, ilmenite, rutile, magnetite, siderite, grunerite and chamosite. Fluorite and calcite occur at all stages. The granites exhibit low Al2O3, Eu, Ba and Sr contents, high Na2O+K2O, Zr+Nb+Ce+Y, 10,000×Ga/Al and Zr values, and high FeOT/(FeOT+MgO) (0.90–0.95) ratios, which are similar to those of typical A-type granites. They also have high whole rock ɛNd(t) values (+3.6 to +6.2) and zircon ɛHf(t) (+6.7 to +17.4). Temperature and oxygen fugacity ( [Formula: see text] ) estimates suggest that the northern Daolinshan A-type granitic magmas were generated at high temperature (960–990°C), low [Formula: see text] (on or slightly above the fayalite-magnetite-quartz (FMQ) buffer), and F- and CO2-rich but extremely H2O-poor conditions, indicating a rifting rather than arc setting for magma formation. Based on the compositions and geochronological and Hf isotope data of Neoproterozoic and older igneous rocks in the region, we suggest that the northern Daolinshan granites were most probably produced by high-temperature melting of slightly earlier tholeiitic rocks underplated in the lower crust as a result of a ∼780Ma high-temperature mantle plume. The results support the hypothesis that the rifting away of South China from Laurentia was initiated by a ca. 780Ma mantle plume during the breakup of Rodinia. The mantle plume activities also caused widespread crustal growth in South China in the Neoproterozoic (830–740Ma).