Tectonic framework and crustal evolution of the Precambrian basement of the Tarim Block in NW China: New geochronological evidence from deep drilling samples

The Jiaojia Fault (JJF) in the Jiaodong area of eastern China is an important NNE-trending structure that is subsidiary to the regional Tancheng–Lujiang (Tan-Lu) Fault Zone, and hosts >1200 t of gold reserves contained in disseminated and stockwork ore, dominantly in the footwall of the fault. We present new zircon U–Pb, apatite fission track, and illite K–Ar data along the JJF and have delineated its tectonic history focusing on its formation and reactivation. Zircon U–Pb dating shows that the Shangzhuang granite is a composite body with ages between 132 ± 1 and 127 ± 1 Ma. Illite K–Ar ages for the fault’s gouge range from 83 ± 2 to 68 ± 2 Ma, and the measured apatite fission track ages for ores are between 55 and 21 Ma. Previous zircon U–Pb geochronology and structural studies suggest that the JJF was originally activated in the Jurassic during 160–150 Ma as a sinistral fault. The JJF was a normal fault in the Early Cretaceous due to NW–SE orientated tension and NE–SW compression, which lasted from 135 to 120 Ma. This was followed by sinistral strike–slip faulting due to NW–SE compression and NE–SW tension during 120–110 Ma, and it changed to normal displacement at ca. 110 Ma. Our apatite fission track data analysis and thermal modeling of representative samples suggest that there was a subsequent dextral reactivation of the fault at ca. 55 Ma. Previous age data of ca. 130–110 Ma for gold mineralization along the JJF coincides with the Early Cretaceous magmatism and is coeval with the transition from normal faulting to sinistral strike–slip faulting of the JJF in Early Cretaceous, which is interpreted to be due to changing direction of the subducting Pacific Plate.

Cretaceous–Cenozoic tectonic history of the Jiaojia Fault and gold mineralization in the Jiaodong Peninsula, China: constraints from zircon U–Pb, illite K–Ar, and apatite fission track thermochronometry

The latest Neoarchean–Paleoproterozoic evolution of the Dunhuang block, eastern Tarim craton, northwestern China: Evidence from zircon U–Pb dating and Hf isotopic analyses

https://www.igm.nsc.ru/labs/lab212/~safonova/pdf/gr-long2012.pdf

Geochemistry and U–Pb detrital zircon dating of Paleozoic graywackes in East Junggar, NW China: Insights into subduction–accretion processes in the southern Central Asian Orogenic Belt

Inhomogeneous lithospheric thinning in the central North China Craton: Zircon U-Pb and S-He-Ar isotopic record from magmatism and metallogeny in the Taihang Mountains

High resolution in situ U-Pb zircon geochronology on zoned grains can obtain isotope signatures from multiple growth or thermal events.We present a method using laser ablation-multicollector-inductively coupled plasma-mass spectrometry(LA-MC-ICP-MS) to overcome complications associated with intricately zoned zircon crystals through in situ sampling of zircon volumes as small as 12 μm,25 μm and 40 μm in diameter by about 10 μm in depth.High precision U-Pb age of a series of zircon standard covering a wide age range of 30 to 1 065 Ma was acquired using LA-MC-ICP-MS.The precision of measured Pb/U ratios in homogeneous zircon is about 2%(2σ),resulting in routinely achieved precision of U-Pb ages obtained by external calibration of～1%(2σ) or better.All masses of interest can be simultaneously recorded with a multi-ion counting system(MIC) operating in static mode,and the short ablation required to achieve such precision results in spatial resolution that is superior to comparable U-Pb zircon analyses by single collector ICP-MS.The resulting present U-Pb age for five zircon reference samples and two geological samples show an excellent agreement with the previously reported ID-TIMS or SHRIMP data.

In situ U-Pb zircon dating using laser ablation-multi ion counting-ICP-MS

Transitional metal isotope is now a new highly focused research point of isotope geochemistry,but its analytical techniques have become the main constraint on its development in recent years. Techniques for high-precision measurements of Cu,Zn isotope ratios using Neptune MC-ICPMS are reported in details in this paper,which include the correction of instrument mass bias,the assessment of matrix effects,and the long-term reproducibility. The reproducibility of the in-house standard IMR Cu and that of IMR Zn in five months are δ65CuNIST 976=(0.34±0.08)‰(2SD,n=32),δ66ZnJMC Zn=(-9.64±0.05)‰(2SD,n=26),δ67ZnJMC Zn= (-14.37±0.16)‰(2SD,n=26) and δ68ZnJMC Zn=(-19.01±0.08)‰(2SD,n=26). A study of these data in comparison with the Cu,Zn isotopes of the reference materials shows that the authors' results are in an excellent agreement with the data available.

Hou Ke

Papers

In situ U-Pb zircon dating using laser ablation-multi ion counting-ICP-MS

High precision Cu,Zn isotope measurements by multi-collector ICP-MS