Zircon Hf-isotopic mapping for understanding crustal architecture and metallogenesis in the Eastern Qinling Orogen
Zircon Hf-isotopic mapping for understanding crustal architecture and metallogenesis in the Eastern Qinling Orogen
复制标题
DOI：
10.1016/j.gr.2017.04.008
复制
发表时间：
2017-10
影响因子：
6.1
通讯作者：
Changming Wang;Jun Deng;L. Bagas;Qiao Wang
中科院分区：
文献类型：
--
作者：
Changming Wang;Jun Deng;L. Bagas;Qiao Wang
东秦岭造山带是位于华北与扬子两大造山带之间的一条重要的复合碰撞带。本文结合与成矿作用有关的岩浆岩的地质和Hf同位素资料，探讨了地壳结构与成矿作用之间的联系，并将找矿重点放在造山带上。嵩县正长花岗岩为225 ± 2 Ma，二长花岗岩为160 ± 1 Ma，方城东部正长花岗岩为108 ± 1 Ma，二长花岗岩为102 ± 1 Ma。将我们的数据与整个EQO的数据相结合，揭示了寒武纪以来的七次主要岩浆事件。这些岩浆活动发生在寒武纪-志留纪与俯冲作用有关的岩浆活动、早泥盆世与碰撞作用有关的岩浆活动、早二叠世-晚三叠世与俯冲作用有关的岩浆活动、晚三叠世碰撞岩浆活动、晚三叠世-早侏罗世碰撞后岩浆活动以及侏罗纪-白垩纪陆内俯冲作用期间的岩浆活动。南召闪长岩和二长花岗岩为− 1.4 ~ 10.9;嵩县正长岩为− 27.1 ~ − 15.6，二长花岗岩为− 27.5 ~ − 25.1;方城东部正长花岗岩为− 12.9 ~ − 3.4。结合Hf同位素数据的EQO从以前的研究中，我们已经评估了Hf同位素组成的时空分布。Hf同位素填图表明，宽坪缝合带是华北与扬子板块的重要构造分界线，它将扬子板块东部的下地壳划分为北部的古老改造下地壳和南部的新生下地壳，并提供了矿床分布的信息。斑岩型和斑岩-矽卡岩型Mo（-W）矿床与岩浆岩有关，岩浆岩侵位在低εHf和高TDMc的区域，代表古老和改造的地壳成分。相比之下，斑岩和斑岩-矽卡岩型Cu（-Mo）矿床与岩浆岩有关，岩浆岩侵位在εHf和TDMc值可变的区域，其特征是主要改造了旧地壳成分，具有少量的年轻物质。岩浆源区具有低εHf、高TDMc的特征，为与花岗岩有关的Mo或Pb-Zn-Ag矿化。
The Eastern Qinling Orogen (EQO) is a major composite collisional zone located between the North China and the Yangtze cratons. This contribution combines geological and Hf–isotopic data from magmatic rocks associated with mineralization to gain insights into links between the crust architecture and metallogeny, and to focus exploration in the orogen.The new zircon U–Pb dates reported in this study are 434 ± 2 Ma for diorite, 433 ± 2 and 436 ± 2 Ma for monzogranite, and 454 ± 2 Ma for granodiorite in the Nanzhao area; 225 ± 2 Ma for syenite and 160 ± 1 Ma for monzogranite at Songxian; and 108 ± 1 and 102 ± 1 Ma for syenogranite in eastern Fangcheng. Combining our data with those from the entire EQO reveals seven major magmatic events since the Cambrian. These magmatic events took place during the Cambrian–Silurian associated with subduction, Early Devonian magmatism related to a collisional event, Early Permian to Late Triassic magmatism related to subduction, Late Triassic collisional magmatism, Late Triassic to Early Jurassic post–collision magmatism, and Jurassic–Cretaceous magmatism during intra–continental subduction.Lu-Hf isotopic data collected from granitic rocks for this study give εHf(t) values of: − 1.4 to 10.9 for diorite and monzogranite at Nanzhao; − 27.1 to − 15.6 for syenite and − 27.5 to − 25.1 for monzogranite at Songxian; and − 12.9 to − 3.4 for syenogranite in the eastern Fangcheng. Combining Hf isotopic data for the EQO from previous studies, we have evaluated the spatio–temporal distribution of Hf isotopic compositions. The resultant Hf isotopic maps highlight the location of the Kuanping Suture as an important tectonic boundary between the North China and the Yangtze cratons, which separates the EQO into a north part with an old and reworked lower crust and a southern part representing a juvenile lower crust.The Hf isotopic mapping of the EQO also provides information on the distribution of mineral deposits. Porphyry and porphyry–skarn Mo(–W) deposits are associated with magmatic rocks were emplaced in zones with low–εHf and high TDMcvalues representing old and reworked crustal components. In contrast, porphyry and porphyry–skarn Cu(–Mo) deposits are associated with magmatic rocks emplaced in domains with variable εHf and TDMcvalues characterized by dominantly reworked old crustal components with minor juvenile material. The magmatic source for the intrusions is characterized by low–εHf and high TDMcvalues, which are granite–related Mo or Pb–Zn–Ag mineralization.