首页|东昆仑印支晚期埃达克质花岗岩的成因和地质意义

东昆仑印支晚期埃达克质花岗岩的成因和地质意义

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东昆仑造山带印支期的碰撞造山过程目前尚存在争议,在东昆仑小南川地区新发现的三叠纪埃达克质花岗岩为约束碰撞造山演化提供了新的地质证据.研究通过对小南川地区出露的磨石沟和本头山2个花岗岩体开展岩石学、地球化学、锆石U-Pb和Lu-Hf同位素分析,探讨其岩石成因和构造环境,并结合以往东昆仑印支晚期岩浆作用和沉积作用的研究成果,初步讨论了东昆仑印支造山带的碰撞造山过程.磨石沟岩体岩性为花岗闪长岩和二长花岗岩,形成时代为209～208 Ma;本头山岩体岩性为花岗闪长岩,形成时代为201～200 Ma.2个岩体的花岗岩含较高的SiO2和A12O3,富碱且相对富钠,同时含较高的Sr(398×10-6～613×10-6)和Sr/Y比值(50～97),亏损重稀土,无Eu异常,表现出埃达克质花岗岩的地球化学特征.磨石沟花岗岩具有负的全岩εNd(t)值(-3.60～-3.34)和变化的锆石εHf(t)值(-1.3～5.9),表明其来源于加厚下地壳的部分熔融.本头山花岗岩具有负的全岩εNd(t)值(-1.65～-1.55)和正的锆石εHf(t)值(+3.4～+7.3),表明其来源于变质基性岩组成的加厚下地壳,残留相为榴辉岩.磨石沟岩体和本头山岩体花岗岩形成于东昆仑印支造山带碰撞后伸展的构造环境.综合分析表明,东昆仑造山带在晚三叠世处于碰撞和碰撞后阶段,而碰撞后阶段的岩浆活动可以进一步划分为晚三叠世早期和晚三叠世晚期—早侏罗世初期2个阶段.
Petrogenesis and geological significance of the Late Indosinian adakitic granites in the East Kunlun Orogen
[Objective]The Indosinian collision process of the East Kunlun Orogenic Belt remains a subject of debate.The newly discovered Triassic adakitic granites in the Xiaonanchuan area of East Kunlun provide new geological evidence that constrains the evolution of collisional orogenesis.[Methods]This study conducted petrological,geochemical,zircon U-Pb,and Lu-Hf isotopic analyses of the Moshigou and Bentoushan granitic intrusions in the Xiaonanchuan area to investigate their petrogenesis and tectonic settings.By integrating previous research on magmatism and sedimentation during the late Indosinian period within the East Kunlun Orogenic Belt,a preliminary discussion was conducted on collisional orogensis process.[Results and Conclusion]The Moshigou intrusion consists of granodiorite and monzogranite with zircon U-Pb ages of 209-208 Ma.The Bentoushan intrusion is composed of granodiorite with zircon U-Pb ages of 201-200 Ma.These granitoids have high SiO2and Al2O3 contents and are rich in sodium.They also have high Sr contents(398×10-6-613× 10-6)and Sr/Y ratios(50-97)and are depleted in heavy rare earth elements without Eu anomalies,exhibiting typical geochemical characteristics of adakitic rocks.The Moshigou granitoids have negative whole-rock εNd(t)(-3.60 to-3.34)and variable zirconεHf(t)(-1.3 to+5.9),indicating their derivation from the partial melting of the thickened lower crust.The Bentoushan granitoids have negative whole-rock εNd(t)(-1.65 to-1.55)and positive zircon εHf(t)(+3.4 to+7.3),suggesting their origin from meta-basic rock-dominated thickened lower crust with eclogite residue.Significance These results suggest that they were formed in a post-collisional extension setting.A comprehensive analysis indicates that the East Kunlun Orogenic Belt was in the collision and post-collision stages during the Late Triassic.The post-collision stage can be further divided into two phases of magmatic activity:early and late phases of the Late Triassic.

collisional orogenesisLate Indosinianpetrogenesisadakitic granitesEast Kunlun

王秉璋、李五福、郑英、王春涛、赵忠国、金婷婷、曹锦山、付长垒

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青海省地质矿产勘查开发局,青海西宁 810008

青藏高原北部地质过程与矿产资源重点实验室,青海西宁 810012

青海省地质调查院,青海西宁 810012

中国科学院大学,北京 100049

中国科学院广州地球化学研究所同位素地球化学国家重点实验室,广东 广州 510640

中国地质科学院地质研究所,北京 100037

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碰撞造山过程 印支晚期 岩石成因 埃达克质花岗岩 东昆仑

第二次青藏高原综合科学考察研究(STEP)项目青海省地质矿产勘查开发局项目青海省地质勘查专项资金项目Geological and Mineral Exploration Project of the Qinghai Provincial Development Bureau

2019QZKK0702地矿[2021]61号2024524015jc015[2021]61

2024

10.12090/j.issn.1006-6616.2024030

地质力学学报
中国地质科学院地质力学研究所

地质力学学报

CSTPCD北大核心
影响因子：0.5
ISSN：1006-6616
年,卷(期)：2024.30(5)