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[Display omitted] • Chlorite at Qulong includes three types of chlorite veins and disseminated chlorite. • The chlorite co-existing with Cu mineralization is high Fe with long wavelength. • The ore fluid evolved to be more acidic and higher silica activity over time. • SWIR and chlorite geochemistry can be combined for porphyry exploration in orogen. The genetic mechanism and exploration model for porphyry deposits in subduction zones has been comprehensively and systematically investigated; in contrast, our understanding for porphyry mineralization in collisional orogeny is limited. Qulong porphyry Cu-Mo deposit, a typical porphyry Cu deposit (PCD) developed in the collisional setting, was chosen as the subject of this study. The study is mainly focused on interpretation of short-wave infrared (SWIR) spectroscopy combined with mineral geochemistry of chlorite from Qulong deposit to guide exploration in future. Hydrothermal alteration in Qulong mineralization system can be divided into three zones, which are the inner potassic alteration zone, the outside propylitic alteration zone and phyllic alteration. Phyllic alteration can be intensively superimposed on the early potassic and prophylitic alteration zones. Chlorite is widely distributed in both of the propylitic and phyllic zones. Four types of chlorite were observed in Qulong deposit, including three stages of vein-related chlorite (Chl-I, Chl-II, Chl-III) and one type of disseminated chlorite (Chl-D). Mineral assemblage of Chl-I stage includes chlorite–anhydrite–pyrite. Minerals in Chl-II stage consist of chlorite–epidote–pyrite–chalcopyrite. Mineral assemblage of Chl-III stage is composed of chlorite–sericite–quartz–chalcopyrite, which is later than both Chl-I and Chl-II. Chl-D was developed mainly by alteration of primary biotite phenocryst. Chl-I, Chl-II and Chl-D were formed along with the propylitic alteration; however, Chl-III is from the phyllic alteration. Chl-II and Chl-III are both closely related with Cu mineralization. The major element compositions of chlorite show a regular variation of Mg# with fluid evolution. Transition from shorter wavelength chlorite (Fe feature around 2250 nm) to longer wavelength goes with the decrease of Mg#, except for Chl-D. In summary, chlorite associated with Cu mineralization in Qulong is mainly occurred in veins and has low Mg# ratios and longer wavelength. Such chlorite is the indicator for Cu mineralization and should be the target in future exploration. In addition to chlorite, sericite in Qulong also shows systematic change from early-stage phengite to late-stage muscovite. In combination of mineral geochemistry and thermodynamic modelling, we suggest that ore-forming fluid gradually evolved to be more acidic with higher silica activity over time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluctuations of Ca/K, Mg/Fe, Sr/Ti, and Si/Al ratios correspond well with orebody. • Wavelength of white micas (2207–2214 nm) and chlorite (2247–2253 nm) corresponds well with mineralization. • Sub-high magnetic susceptibility correlates with mineralization. • Low resistivity delineates the superimposed part of argillic alteration on phyllic alteration zone. With the increasing demand for copper resources, exploration methods based on the discovered porphyry Cu deposits (PCDs) to target concealed orebodies are of greater importance. Single parameter is no longer sufficiently effective against concealed deposit exploration, and different combinations of survey techniques are required. The Qulong porphyry Cu-Mo deposit is the largest collisional PCD found in China. Here we evaluated the relationship between variations in multiple parameters and alteration to define exploration footprints around the porphyry Cu centers. In order to improve the exploration efficiency and accuracy, we combined geophysical (magnetic susceptibility and resistivity) and popular geochemical exploration methods (i.e., short wavelength infrared spectroscopy- SWIR, portable X-ray fluorescence- pXRF, and indicator minerals) to the drill hole ZK005 of Qulong PCD in southern Tibet seeking for a firm interpretation. Four orebody indicators were established in study of Qulong deposit, which are: (i) the fluctuations of Ca/K, Mg/Fe, Sr/Ti, and Si/Al ratios, (ii) long-wavelength white mica (2207–2214 nm) and short-wavelength chlorite (2247–2253 nm), (iii) sub-high magnetic susceptibility and (iv) low resistivity. Multi-scale prospecting methods can improve prospecting efficiency and narrow down the target area. Based on the local environment, selecting an appropriate combination of methods can improve exploration efficiency in the brownfields at a lower cost. [ABSTRACT FROM AUTHOR]