Ridge subduction identified within the ancient Tianshan Ocean: Evidence from temporal variations of magmatism in the Tuwu-Yandong porphyry Cu belt, NW China

IF 3.2 2区 地球科学 Q1 GEOLOGY
Yun-feng Wang , Bing Xiao , Shuqi Gao , Wei Wang
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引用次数: 0

Abstract

Our knowledge of the many magmatic episodes and porphyry Cu belts north of the Kangguer Shear Zone in the Eastern Tianshan region is complicated by the ongoing controversy over the mechanism of the Tianshan Oceanic plate subducting during the Carboniferous epoch. Within the well-known Tuwu–Yandong porphyry Cu belt, we offer new zircon U–Pb dates, Hf isotopes, whole-rock geochemistry, and whole-rock Sr–Nd isotopes for granite porphyry, quartz diorite porphyry, and diorite. These findings shed light on I- and A-type granitoids as well as slab-derived adakites, offering fresh perspectives on the Tianshan Oceanic plate’s subduction process. The majority of the adakites are diorite and quartz diorite porphyry (334–331 Ma), which have low Y and Yb contents, high Sr concentrations, and higher Sr/Y ratios. These rocks yielded high positive zircon εHf(t) values (+10.3 to +14.1) and whole-rock εNd(t) (+6.8 to +7.5) values. The adakitic diorite is thought to originate from the melting of the oceanic slab, while the subsequent quartz diorite porphyry formed through fractional crystallization of the dioritic magma. The A-type granite porphyry (331 Ma) displays high contents of SiO2 and Fe2O3T, along with increased Zr concentrations and zircon saturation temperatures. This rock type also possesses zircon εHf(t) (+10.5 to +11.8) and whole-rock εNd(t) (+6.4 to +6.6) values, derived from the partial melting of the juvenile crust. The late I–type granite porphyry (322 Ma) is characterized by high SiO2 and low P2O5 contents, as well as positive εHf(t) values (+9.5 to +13.2) and whole-rock εNd(t) values (+5.9 to +7.0). These rocks originated from the juvenile crust and underwent significant fractional crystallization. Our new data suggest that the ancient Tianshan Oceanic plate experienced a slab window during its northward subduction in the Carboniferous, creating a regional extensional setting. Through a detailed analysis of temporal variations in the regional magmatic rocks, we identified a distinguishable rock association of Nb-enriched, high-Mg, slab-derived adakites, and A-type rocks in the northern area of the Kangguer Shear Zone between 340 and 330 Ma. These rocks, along with the coeval regional porphyry Cu deposits, indicate the occurrence of a ridge subduction during that time.

Abstract Image

在古天山洋内发现海岭俯冲:中国西北部图乌-燕东斑岩铜矿带岩浆活动的时间变化证据
石炭世天山洋板块俯冲机制的争论,使我们对东天山地区康格尔剪切带以北许多岩浆期和斑岩铜带的认识复杂化。在著名的吐乌—延东斑岩铜带中,我们提供了新的花岗岩斑岩、石英闪长斑岩和闪长岩的锆石U-Pb测年、Hf同位素、全岩地球化学和全岩Sr-Nd同位素。这些发现揭示了I型和a型花岗岩以及板源埃达岩,为研究天山大洋板块的俯冲过程提供了新的视角。埃达奇岩主要为闪长岩和石英闪长斑岩(334 ~ 331 Ma),具有低Y、低Yb含量、高Sr浓度和较高Sr/Y比值的特征。这些岩石的锆石εHf(t)值为+10.3 ~ +14.1,全岩εNd(t)值为+6.8 ~ +7.5。埃达克闪长岩被认为起源于大洋板块的熔融作用,而随后的石英闪长斑岩则是闪长岩岩浆的分离结晶作用形成的。a型花岗斑岩(331 Ma) SiO2和Fe2O3T含量较高,Zr浓度升高,锆石饱和温度升高。锆石εHf(t)值为+10.5 ~ +11.8,全岩εNd(t)值为+6.4 ~ +6.6。晚i型花岗斑岩(322 Ma)具有高SiO2、低P2O5含量、正εHf(t)值(+9.5 ~ +13.2)和全岩εNd(t)值(+5.9 ~ +7.0)的特征。这些岩石起源于幼年地壳,并经历了显著的分离结晶。新资料表明,古天山大洋板块在石炭世向北俯冲过程中经历了板块窗期,形成了区域伸展环境。通过对区域岩浆岩时间变化的详细分析,在340 ~ 330 Ma之间,我们在康格尔剪切带北部地区发现了一个明显的富铌、高镁、板源埃达克岩和a型岩石组合。这些岩石,连同同时期的区域斑岩型铜矿床,表明在这一时期发生了脊状俯冲。
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来源期刊
Ore Geology Reviews
Ore Geology Reviews 地学-地质学
CiteScore
6.50
自引率
27.30%
发文量
546
审稿时长
22.9 weeks
期刊介绍: Ore Geology Reviews aims to familiarize all earth scientists with recent advances in a number of interconnected disciplines related to the study of, and search for, ore deposits. The reviews range from brief to longer contributions, but the journal preferentially publishes manuscripts that fill the niche between the commonly shorter journal articles and the comprehensive book coverages, and thus has a special appeal to many authors and readers.
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