Magmatic Evolution and Mineralization of Porphyry Copper-Gold Deposits in the Duolong Ore Concentration Area, Tibet

The Bangong Lake-Nujiang River metallogenic belt is located between the Qiangtang Block and Lhasa Block, and the Duolong ore concentration area is located in the western section of the Bangong Lake-Nujiang River metallogenic belt. Till now, several large and super large copper-gold deposits, such as Duobuza, Bolong, Dibaonamugang, Naruo and Rongna deposits have been discovered in this area, mainly porphyry copper-gold ones.

The Late Cretaceous Crustal Magmatism of the Geza Arc Metallogenic Belt in Yunnan Province,and Zircon Ages and Hf Isotopic Evidence of the Porphyry Cu-Mo Mineralization

Objective The Geza arc in Yunnan Province,located in the southern Yidun arc,is an important part of the Sanjiang tectonic-magmatic belts in southwestern China and is a newly discovered copper polymetallic ore-concentrating district.Recent studies show that the newly discovered Yanshanian porphyry Cu-Mo polymetallic mineralization superimposed in the Indosinian porphyry copper belt in this area.

Alteration and Mineralization Types of the Laurani Porphyry Deposit in Central-Andean Metallogenic Belt, Bolivia

1 Introduction The Laurani porphyry deposit is located in the Altiplano,an extensive North-South trending structural basin that formed in Central-Andean metallogenic belt,Bolivia.The Altiplano poly-metallic province contains sub-volcanic ore

The Yanshanian Granites and Associated Mo-Polymetallic Mineralization in the Xiangcheng-Luoji Area of the Sanjiang-Yangtze Conjunction Zone in Southwest China

The Xiangcheng-Luoji area is located in the conjunction of the southern part of the ＂Sanjiang＂ mineralization belt and the west margin of Yangtze craton. The geological studies were carried out to know the Indosinian large porphyry Cu polymetallic deposits. Recent studies revealed that the area existed in the superposition of Late Yanshanian acidic intrusive rock belt and developed Mo-Cu polymetallic mineralization where promising exploration results have been achieved. Through the systematic study of geochronology, formation age of the Renlin Mo-minieralization monzogranite is 81.7±1.1 Ma. Re-Os dating results concentrate on 82.34±1.2–88.27±1.23 Ma for the model ages of molbdenite of Tongchanggou Mo deposits, average age is 85 ± 2 Ma where seven data points constitute a good isochron which shows that they were the same period products of mineralization. Geochemical features shown that the rocks have a high content of SiO 2（66.59–77.36wt%）, alkaline-rich（K2O=2.68–6.08wt%; Na2O=0.50–4.91wt%; K2O/Na2 O ratios are 0.71–5.56, where average ratio of 1.89） and have aluminum–rich features（Al2O3 10.38–15.15wt%） with σ values less than 3.3. Which indicate that they belong to the high-K calc-alkali to shoshonite series. Geochemistry of Yanshanian intrusions shows that rocks are enrich in LREE with obvious negative δEu anomalies, enrichment of trace elements like, LILE elements（Rb, Th, Ba） with a relative loss of Ba, and loss of high field strength elements（Nb, Ta, P, Ti） and HREE elements. The granite genetic classification diagram shows that the granites belong to A-type granite and formatted in syn-collision tectonic environment. Meanwhile, the Yanshanian granites also inherited the characteristics of island arc environment which formed in the process of crustal melting caused by upwelling of asthenospheric substances in the extensional tectonic background. The process of partial melting existed substances from the deep（lower crust or upper mantle） which have been added. In the Xiangcheng-Luoji area, monzogranite and granodiorite porphyry bodies are widely developed Mo polymetallic mineralization, the deep porphyry mineralization have great potential for geological prospecting.

AIRRLS: An Augmented Iteratively Re-weighted and Refined Least Squares Algorithm for Inverse Modeling of Magnetometry Data

This work aims to examine the functionality of a new Augmented Iteratively Re-weighted and Refined Least Squares algorithm(AIRRLS)to generate a 3D model of magnetic susceptibility property from a potential field magnetometry survey.Whereby this algorithm ameliorates an lp norm Tikhonov regularization cost function through replacing a set of weighted linear system of equations.It leads to constructing a magnetic susceptibility model that iteratively converges to an optimum solution,meanwhile the regularization parameter performs as a stopping criterion to finalize the iterations.To tackle and suppress the intrinsic tendency of a sought target responsible for generating a magnetic anomaly and to not be imaged at shallow depth in inverse modeling,a prior depth weighting function is imposed in the principle system of equations.The significance of this research lies in improvement of the performance of the inversion,where the running time of an lp norm problem after incorporating a pre-conditioner conjugate gradient solver(PCCG)in cases of large scale geophysical dataset.Forasmuch as this study attempts to image a geological target with low magnetic susceptibility property,it is assumed that there is no remanent magnetization.The applicability of the algorithm is tested for a synthetic multi-source data to demonstrate its performance in 3D modeling.Subsequently,a real case study in Semnan province of Iran,is investigated to image an embedded porphyry copper layer in a sequence of sediments.The sought target consists of a concealed arc-shaped porphyry andesite unit that may have potential of Cu occurrences.Results prove that it extends down at depth,so exploratory drilling is highly recommended to get insights about its potential for Cu-bearing mineralization.

Porphyry mineralization in the Tethyan orogen

The Tethyan metallogenic domain(TMD),as one of the three major domains in the world,extends over 10000 km from east to west,and has developed several world-class metallogenic belts,such as the Gangdese porphyry Cu belt,the Sanjiang metallogenic belt,the Iran porphyry Cu belt,the Pakistan porphyry Cu belt,the southeastern European epithermal gold deposit belt,and the Southeast Asian Sn belt.The formation and evolution of the TMD is mainly controlled by the multi-stage subduction of Tethys oceanic slabs,the opening and closing of several small ocean basins,and continent-continent collision.The Tethys oceans include the Proto-Tethys(Cambrian-Silurian),Paleo-Tethys(Carbonaceous-Triassic)and Neo-Tethys(Jurassic to Cretaceous),which in turn are formed by rifting from the Gondwana land at different times in different micro-continents.With a series of geological processes such as oceanic opening and closing,continental collision and post-collisional reworking with intraplate deformation,various types of ore deposits are developed in the TMD,including porphyry deposits,epithermal deposits,VMS deposits,chromite deposits,Sn deposits and orogenic gold deposits.The metallogenic processes of the TMD can be categorized into three stages.(1)Oceanic subduction:With the subduction of the oceanic slab and dehydration of basalt and sediments,the asthenospheric mantle was metasomatized with preliminary enrichment in metals under oxidized condition.(2)Continental subduction:Continental collision induced partial melting of the mantle wedge enriched the metals and water in mafic melts,which ascended from subarc depths to the lower crust,locally to the shallow crust for hydrothermal mineralization.(3)Post-collisional reworking:Partial melting of the mafic intrusives in the lower crust produced felsic melts under oxidized and water-rich conditions,which underwent crystal fractionation and transferred water and metals into hydrothermal fluids for mineralization.The large-scale porphyry mineralization in the TMD mainly occurs in the Miocene,which is an important scientific issue worthy of further study in the future.How is the metal enriched in the processes of gradual maturity of the crust,and how does large-scale mineralization occur in a collisional orogen where there is no subduction and dehydration of oceanic slabs anymore to supply S and Cl?These are still important questions in the study of porphyry mineralization in the Tethyan orogen.The application of hyperspectral and mineralogical studies of alteration assemblages is beneficial for prospecting and exploration in the TMD.