Research on the Application of Residual Apparent Polarization to Surveying Deep Jiaojia-type Gold Mines

The theory and equations of the residual apparent polarization method are proposed and described in this article. Based on studies of existing mines, the residual apparent polarization ηα^sy, calculated from the induced-current middle-gradient apparent polarizations ηα^sy at large and small electrode spaces over the known deep Jiaojia-type gold mines, have been shown to separate the effects of mines from the anomalous polarizations generated from the strongly altered rocks in fracture zones.

Apparent Polar Wander Path from the Tarim Block in China

The apparent polar wander (APW) path from the Tarim block consists of palaeo-magnetic poles ofDevonian (λ=16°N, ψ= 165° E. A_(95)=4°). Late Carboniferous (λ=41° N, ψ=160° E, A_(95)=4°).Permian (λ=61°N, ψ=177° E. A_(95)=9°). Early Triassic (λ=69° N. ψ=183° E. A_(95)=11°) andJurassic/Cretaceous (λ=65° N, ψ=214° E. A_(95)=6°) times. On the basis of this APW path, it is con-cluded that the Tarim block was subducted beneath the Kazakstan plate between Devonian and Permiantimes. The Tarim, North China and South China blocks were sutured between the Early Triassic and EarlyCretaceous. Tarim had moved eastward some 2000 km relative to Siberia since the Cretaceous.

PALEOMAGNETISM OF THE LATE CRETACEOUS AND EARLY TERTIARY ROCKS FROM FILDES PENINSULA,WEST ANTARCTICA, AND ITS GEOTECTONIC SIGNIFICANCE

The paleomagnetis m of 109 oriented samples collected from drill cores through 5 rock units of Late Cretaceous and Early Tertiary on Fildes Peninsula were systematically studied-According to the study, the paleomagnetic pole position of this area is different from the position of Australia during the 55-45 Ma period. This means that when the break - up of the Gondwanaland at 55 - 45 Ma ago, Australia was separated from the Gondwanaland, drifting southward 20°-30°Lat. and rotating 70°-80°westward and then gradually arriving at recent position . The paleolatitudinal data indicate that it is not impossible that the area studied was covered with land glacier at that time. The apparent polar wander path of Antarctica through the geological time are also roughly worked out.

True polar wander in the Earth system

True polar wander(TPW),or planetary reorientation,is the rotation of solid Earth(crust and mantle)about the liquid outer core in order to stabilize Earth’s rotation due to mass redistribution.Although TPW is well-documented on Earth presently with satellites and for multiple planets and moons in the Solar System,the prevalence of TPW in Earth history remains contentious.Despite a history of controversy,both the physical plausibility of TPW on Earth and an empirical basis for it are now undisputed.Lingering resistance to the old idea likely stems from the fact that,like plate tectonics,TPW may influence much of the Earth system,thus acknowledging its existence requires rethinking how many different datasets are interpreted.This review summarizes the development of TPW as a concept and provides a framework for future research that no longer regards TPW like a ghost process that may or may not exist,but as an integral part of the Earth system that can relate shallow and deep processes that are otherwise only mysteriously linked.Specifically,we focus on the temporal regularity of large TPW,and discuss its relationship with the supercontinent-megacontinent cycle based on previous studies.We suggest the assembly of megacontinents has a close linkage to large TPW.Meanwhile,supercontinent tenure and breakup have a close linkage to fast TPW.The effects of TPW on sea level changes,paleoclimate,biological diversity,and other facets of the Earth system are presented and require interdisciplinary tests in the future.

The influence of Cretaceous paleolatitude variation of the Tethyan Himalaya on the India-Asia collision pattern

Identifying when, where, and how India and Asia collided is a prerequisite to better understand the evolution of the Himalayan-Tibetan Plateau. Whereas with essentially the same published paleomagnetic data, a large range of different India-Asia collision models have been proposed in the literature. Based upon the premise of a northwards-moving Indian plate during the Cretaceous times, we analyze the significant variations in relative paleolatitude produced by a nearly 90° counterclockwise(CCW)rotation of the plate itself during the Cretaceous. Interestingly, recent studies proposed a dual-collision process with a Greater India basin or post-Neo-Tethyan ocean for the India-Asia collision, mainly in the light of divergent Cretaceous paleolatitude differences of the Tethyan Himalaya between the observed values and expected ones computed from the apparent polar wander path of the Indian plate. However, we find that these varied paleolatitude differences are mainly resulted from a nearly 90° CCW rotation of a rigid/quasi-rigid Greater Indian plate during the Cretaceous. On the other hand, when the Indian craton and Tethyan Himalaya moved as two individual blocks rather than a united rigid/quasi-rigid Greater Indian plate before the India-Asia collision, current available Cretaceous paleomagnetic data permit only multiple paleogeographic solutions for the tectonic relationship between the Indian plate and the Tethyan Himalayan terrane. We therefore argue that the tectonic relationship between the Indian plate and the Tethyan Himalayan terrane cannot be uniquely constrained by current paleomagnetic data in the absence of sufficient geological evidence, and the so-called Greater India basin model is just one of the ideal scenarios.