Ballooning emplacement and alteration of the Chah-Musa subvolcanic intrusion (NE Iran) inferred from magnetic susceptibility and fabric

Abstract

The porphyritic diorite Chah-Musa subvolcanic intrusion is located in the Toroud-Chah Shirin magmatic arc in the northern Central Iranian structural zone. The elliptical Chah-Musa body hosts a copper deposit and intrudes an Eocene sequence of volcanic breccia, agglomerate and red tuffaceous sediment. High magnetic susceptibility values are attributed to the presence of magnetite as a magnetic carrier. Changes in bulk magnetic susceptibility correlate with zonation of alteration in the intrusion. Although the degree of anisotropy of magnetic susceptibility decreases due to hydrothermal alteration, the field observations confirm that this parameter can be used as a strain marker. Strongly oblate magnetic ellipsoids are found in the eastern half of the intrusion where isolated outcrops of flat-lying tuffaceous host cover dioritic rocks (roof zone). Stations with prolate ellipsoids mostly belong to the centre of the intrusion where the magnetic lineations plunge steeply. They are interpreted as indicating the main feeder zone. The concentric fabric pattern at the periphery of intrusion, the oblate magnetic ellipsoids at the roof, the highest anisotropy degree along the small diameter of the intrusion, and an intense deformation of the host rocks, especially at the western margin, all are evidence that the intrusion was ballooning during the late stages of its emplacement. Ascent and emplacement of the Chah-Musa body is ascribed to the tensional space provided by a dextral shear zone created by the regional left-lateral movement on the bounding Anjilow and Toroud strike-slip faults.

Machine Learning (ML)-Based Copper Mineralization Prospectivity Mapping (MPM) Using Mining Geochemistry Method and Remote Sensing Satellite Data

“…In this block, NE-SW-trending volcano-intrusive rocks are composed of middle-to upper Eocene andesites and dacites, and Oligocene diorites. Middle-to late Eocene igneous activity include: (i) local andesitic lava flows associated with marls, tuffaceous marlstones, sandstones, and explosively deposited rhyolitic to rhyodacitic tuffs; (ii) basaltic andesite and lava flows, and pyroclastic rocks of andesite, trachy-andesite; (iii) hypabyssal intrusive rocks and subordinate dacitic-rhyodacitic rocks [63,68]. The faults and fractures controlled ore mineralization in the TCS belt, e.g., [60,61].…”

“…The mineralization system is connected to the evolution of hydrothermal fluid mineralization and mixing with cold and low salinity meteoric water resulting in disseminated-veinlet copper mineralization at deep zones, and vein-type copper, zinc, and lead at shallow zones. This has led to the development of elemental and mineralogical zonation [63]. Despite its importance, geologic information about the Chah-Musa deposit is scarce [64].…”

“…The Chah-Musa deposit is an active mine. The Chah-Musa porphyritic hornblende diorite subvolcanic intrusion is positioned in the eastern part of the TSC belt [62,63]. It is emplaced into the Eocene volcanic sequence.…”

“…The NE-trending Toroud-Chah Shirin (TCS) belt is placed in the Alborz magmatic belt in the north of Iran [58][59][60][61] (Figure 1). A few studies were conducted in the TCS belt and most of the acquired information is only related to depths of less than 100 m [59][60][61][62][63][64]. Exploration for new deep, concealed, and economic ore resources (mineral deposits) in the TCS belt is challenging owing to the insufficiency of comprehensive geological datasets and arid and mountainous geochemical landscapes [15,35,[65][66][67].…”

Magnetic Fabric and Paleomagnetic Analyses of the Zaghar and Tafresh Areas, Central Urumieh-Dokhtar Magmatic Arc, Iran

“…It is regarded as the best tool compared to other traditional fabric measurements for evidencing concealed fabric in poorly oriented rocks, such as magmatic rocks [2]. AMS has been used in particular to characterize the primary magmatic flows and/or the location of preferential pathways for the magma ascent of plutonic, volcanic, and subvolcanic rocks, e.g., in [3,4]. Many publications have widely demonstrated its usefulness in all types of rocks (granites, high metamorphic rocks, dykes, and sedimentary sequences, e.g., [1,[5][6][7][8]).…”