نهشت کانی سپرده های معدنی

 نهشت کانی، سپرده معدنی (Mineral Deposits)

سپرده معدنی ، تجمیع یک ماده معدنی با غلظت غیرمعمول بالا را گویند.

حدود نیمی از عناصر کیمیایی شناخته شده دارای برخی ازخواص فلزی هستند. گرچه اصطلاح فلز فقط برای آن دسته ازعناصر شیمیایی اختصاص داده شده است که دارای دو یا چند مورد از خصوصیات فیزیکی مشخص فلزات (کدورت ، تورق، انعطاف پذیری، قابلیت ذوب) هستند وهمچنین رساناهای (conductors) خوبی برای گرما و برق هستند. تقریباً 40 فلز از طریق استخراج و ذوب مواد معدنی که در آنها موجود اند در دسترس قرار می گیرند.

 انواع خاصی از مواد معدنی را می توان با آسودگی بیشتری نسبت به بقیه ذوب کرد؛ که معمولاً بنام مواد معدنی یاد میشوند. مواد معدنی معدنی تمایل دارند که در توده های سنگی محلی و کوچک متمرکز شوند که در نتیجه فرآیندهای خاص زمینی تشکیل می شوند و به این غلظت های محلی رسوبات معدنی گفته می شود. سپرده های معدنی همان چیزی هستند که جستجوگران به دنبال آن هستند. اصطلاحات کانه (ore mineral) و سپرده معدنی در اصل فقط برای کانی یا منرال ها و مواد معدنی که فلزات از آنها بازیابی می شد مورد استفاده قرار می گرفت، اما استفاده فعلی شامل چند ماده معدنی غیر فلزی.مانند باریت و فلوریت نیز میشود که در عین رسوبات معدنی فلزی یافت می شوند.

هیچ رسوبی به طور کامل تشکیل شده از یک ماده معدنی واحد است. این ماده معمولاً آمیخته با منرال های بی ارزش مجموعاً عنوان باطله (Gangue) معدنی شناخته می شود هستند. هر چه ماده معدنی سنگ متمرکزتر باشد، ذخایر معدنی آن از ارزش بیشتری برخوردار است. برای هر سپرده معدنی جمعی شرایط مانند؛ سطح تکاثف و اندازه سپرده معدنی،‌ که باید نایل شوند تا سپرده با سود کار شود. سپرده معدنی که به اندازه کافی غنی باشد تا بتواند با سود کار شود بنام ذخیره معدنی یاد میشود، و در یک ذخیره معدنی منرال با باطله یکجا بنام کانسنگ یاد میشود.  

تمام ذخایر معدنی سپرده معدنی هستند، اما عکس این درست نیست. ذخیره معدن یک اصطلاح اقتصادی است، در حالیکه سپرده معدنی یک اصطلاح زمین شناسی است. اینکه یک سپرده معدنی معین نیز یک ذخیره معدنی باشد، به عوامل دیگری غیر از سطح تکاثق و اندازه کانسار بستگی دارد؛ همه عواملی که بر استخراج ، فرآوری و حمل و نقل سنگ معدن تأثیر میگذارند نیز باید در نظر گرفته شوند. از جمله این عوامل می توان به شکل سپرده ، عمق آن در زیر سطح ، فاصله جغرافیایی آن، دسترسی به حمل و نقل ، ثبات سیاسی منطقه و عوامل بازار مانند قیمت فلز در تجارت جهانی و هزینه های استقراض پول مورد نیاز برای توسعه یک معدن اشاره کرد. از آنجا که عوامل بازار بطور مداوم تغییر می کنند، ممکن است یک سپرده معدنی معین بعضا یک ذخیره معدنی باشد، اما در مواقعی دیگر ممکن است غیر اقتصادی باشد و از این رو ذخیره معدنی نمیباشد.

کانسارهای معدنی هم در سنگ هایی که در زیر اقیانوس ها قرار دارند و هم در سنگ هایی که قاره ها را تشکیل می دهند، یافت شده است ، اگرچه در واقع کانسارهایی که استخراج شده اند، در سنگ های تنها قاره ای هستند .(استخراج سپرده اقیانوسی مسئله آینده است.) ضخامت پوسته قاره به طور متوسط 35-40 کیلومتر( 20-25 میل) است و زیر پوسته (Crust) گوشته (Mantel) قرار دارد. رسوبات

 معدنی ممکن است در گوشته وجود داشته باشند، اما با استفاده از فناوری حاضر امکان کشف آنها وجود ندارد.


Miner deposit


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