Method for judging formation time of fragmental rock based on structural thermal evolution history

Abstract

The invention provides a method for judging the formation time of fragmental rock based on structural thermal evolution history, which comprises the steps of: firstly, testing a fragmental rock sample by means of fission track to obtain the date of apatite and zircon in the sample; ensuring an analog thermal history route search time region and selecting an analog annealing mode according to the statistics detection probability P (*2) of apatite and zircon; respectively inputting the apatite data, the thermal history route search maximum time region and the annealing mode into thermal history analog software; setting each boundary point in the thermal history route search time region according to the tested track age of the apatite and the zircon and a region construction thermal event; selecting a monte carlo hermal history analog numerical value method; selecting 10000 analog thermal history routes; repeating the analog for 5-8 times; selecting an optimal thermal history route with larger detection values such as GOF and K-S; and analyzing the selected thermal history route to judge the formation time of the sample. The method has low use requirement and wide use range.

Description

technical field [0001] The invention relates to the field of determining the formation age of clastic rocks, in particular to a method for determining the formation age of clastic rocks based on the structural thermal evolution history. technical background [0002] Determination of the age of clastic rock deposition is the key to discussing its formation and evolution, correct stratigraphic correlation, scientific understanding of regional tectonic evolution and regional resource evaluation. At present, people mostly start from the comparison of lithofacies and environment of clastic rocks, the comparison of clastic structures and components, the comparison of rock geochemical characteristics, the age of clastic provenance, the age of top and bottom strata, paleontological fossils and assemblages, isotope dating of volcanic rock interlayers, Cosmic dust dating, dating of authigenic rock minerals in cement, paleomagnetic dating of phase-change sandstones in the same period, ...

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Problems solved by technology

[0005] However, for clastic rocks with inconspicuous bedding and limited exposure, such as conglomerate, magnetic stratigraphic studies are difficult to carry out; conventional lithology, lithofacial comparison, contact relationship, and provenance age analysis are often limited due to conglomerate distribution, The top-bottom boundaries are too wide to be applied; the clastic age cannot represent the sedimentary age; although early authigenic cement minerals can represent the sedimentary age, it is difficult to obtain sufficient samples, and the isotope system of diagenetic dating minerals cannot be confirmed Whether it remained closed during the later thermal events; paleontological fossils in the gravel are scarce, the distribution of volcanic interlayers and cosmic dust is limited, and the sample volume is small and cannot be separated well; the dating method of Cenozoic cement is not suitable for Mesozoic clastic rocks

The above-mentioned methods for determining the depositional age of clastic rocks have certain defects, which makes the formation age of some clastic rocks, especially some conglomerates with limited distribution areas and lack of paleontological fossils, have been controversial, and it is still unresolved.

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